diff --git a/src/Base.php b/src/Base.php
new file mode 100644
index 000000000..3e7f8954e
--- /dev/null
+++ b/src/Base.php
@@ -0,0 +1,67 @@
+<?php
+
+declare(strict_types=1);
+
+namespace drupol\collection;
+
+use drupol\collection\Contract\Base as BaseInterface;
+use drupol\collection\Iterator\ClosureIterator;
+
+/**
+ * Class Base.
+ */
+abstract class Base implements BaseInterface
+{
+    /**
+     * @var \Closure
+     */
+    protected $source;
+
+    /**
+     * Base constructor.
+     *
+     * @param \Closure|iterable|mixed $data
+     */
+    public function __construct($data = [])
+    {
+        switch (true) {
+            case $data instanceof \Closure:
+                $this->source = $data;
+
+                break;
+            case \is_iterable($data):
+                $this->source = static function () use ($data) {
+                    foreach ($data as $k => $v) {
+                        yield $k => $v;
+                    }
+                };
+
+                break;
+
+            default:
+                $this->source = static function () use ($data) {
+                    foreach ((array) $data as $k => $v) {
+                        yield $k => $v;
+                    }
+                };
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getIterator(): ClosureIterator
+    {
+        return new ClosureIterator($this->source);
+    }
+
+    /**
+     * @param array $data
+     *
+     * @return \drupol\collection\Contract\Base
+     */
+    public static function with($data = []): BaseInterface
+    {
+        return new static($data);
+    }
+}
diff --git a/src/Collection.php b/src/Collection.php
index 1246c4139..484250264 100644
--- a/src/Collection.php
+++ b/src/Collection.php
@@ -4,9 +4,9 @@
 
 namespace drupol\collection;
 
+use drupol\collection\Contract\Base as BaseInterface;
 use drupol\collection\Contract\Collection as CollectionInterface;
 use drupol\collection\Contract\Operation;
-use drupol\collection\Iterator\ClosureIterator;
 use drupol\collection\Operation\All;
 use drupol\collection\Operation\Append;
 use drupol\collection\Operation\Apply;
@@ -46,43 +46,8 @@
 /**
  * Class Collection.
  */
-class Collection implements CollectionInterface
+final class Collection extends Base implements CollectionInterface
 {
-    /**
-     * @var \Closure
-     */
-    protected $source;
-
-    /**
-     * Collection constructor.
-     *
-     * @param mixed $data
-     */
-    public function __construct($data = [])
-    {
-        switch (true) {
-            case $data instanceof \Closure:
-                $this->source = $data;
-
-                break;
-            case \is_iterable($data):
-                $this->source = static function () use ($data) {
-                    foreach ($data as $k => $v) {
-                        yield $k => $v;
-                    }
-                };
-
-                break;
-
-            default:
-                $this->source = static function () use ($data) {
-                    foreach ((array) $data as $k => $v) {
-                        yield $k => $v;
-                    }
-                };
-        }
-    }
-
     /**
      * {@inheritdoc}
      */
@@ -93,52 +58,42 @@ public function all(): array
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function append(...$items): CollectionInterface
+    public function append(...$items): BaseInterface
     {
-        return $this::with($this->run(new Append($items)));
+        return new Collection($this->run(new Append($items)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function apply(callable ...$callables): CollectionInterface
+    public function apply(callable ...$callables): BaseInterface
     {
-        return $this::with($this->run(new Apply(...$callables)));
+        return new Collection($this->run(new Apply(...$callables)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function chunk(int $size): CollectionInterface
+    public function chunk(int $size): BaseInterface
     {
-        return $this::with($this->run(new Chunk($size)));
+        return new Collection($this->run(new Chunk($size)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function collapse(): CollectionInterface
+    public function collapse(): BaseInterface
     {
-        return $this::with($this->run(new Collapse()));
+        return new Collection($this->run(new Collapse()));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function combine($keys): CollectionInterface
+    public function combine($keys): BaseInterface
     {
-        return $this::with($this->run(new Combine($keys)));
+        return new Collection($this->run(new Combine($keys)));
     }
 
     /**
@@ -159,22 +114,18 @@ public function count(): int
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
     public static function empty(): CollectionInterface
     {
-        return new static();
+        return new Collection();
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function filter(callable ...$callbacks): CollectionInterface
+    public function filter(callable ...$callbacks): BaseInterface
     {
-        return $this::with($this->run(new Filter(...$callbacks)));
+        return new Collection($this->run(new Filter(...$callbacks)));
     }
 
     /**
@@ -187,32 +138,26 @@ public function first(callable $callback = null, $default = null)
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function flatten(int $depth = \PHP_INT_MAX): CollectionInterface
+    public function flatten(int $depth = \PHP_INT_MAX): BaseInterface
     {
-        return $this::with($this->run(new Flatten($depth)));
+        return new Collection($this->run(new Flatten($depth)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function flip(): CollectionInterface
+    public function flip(): BaseInterface
     {
-        return $this::with($this->run(new Flip()));
+        return new Collection($this->run(new Flip()));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function forget(...$keys): CollectionInterface
+    public function forget(...$keys): BaseInterface
     {
-        return $this::with($this->run(new Forget($keys)));
+        return new Collection($this->run(new Forget($keys)));
     }
 
     /**
@@ -223,14 +168,6 @@ public function get($key, $default = null)
         return $this->run(new Get($key, $default));
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function getIterator(): ClosureIterator
-    {
-        return new ClosureIterator($this->source);
-    }
-
     /**
      * {@inheritdoc}
      */
@@ -241,22 +178,18 @@ public function implode(string $implode = ''): string
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function intersperse($element, int $every = 1, int $startAt = 0): CollectionInterface
+    public function intersperse($element, int $every = 1, int $startAt = 0): BaseInterface
     {
-        return $this::with($this->run(new Intersperse($element, $every, $startAt)));
+        return new Collection($this->run(new Intersperse($element, $every, $startAt)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function keys(): CollectionInterface
+    public function keys(): BaseInterface
     {
-        return $this::with($this->run(new Keys()));
+        return new Collection($this->run(new Keys()));
     }
 
     /**
@@ -269,112 +202,90 @@ public function last()
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function limit(int $limit): CollectionInterface
+    public function limit(int $limit): BaseInterface
     {
-        return $this::with($this->run(new Limit($limit)));
+        return new Collection($this->run(new Limit($limit)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function map(callable ...$callbacks): CollectionInterface
+    public function map(callable ...$callbacks): BaseInterface
     {
-        return $this::with($this->run(new Walk(...$callbacks), new Normalize()));
+        return new Collection($this->run(new Walk(...$callbacks), new Normalize()));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function merge(...$sources): CollectionInterface
+    public function merge(...$sources): BaseInterface
     {
-        return $this::with($this->run(new Merge($sources)));
+        return new Collection($this->run(new Merge($sources)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function normalize(): CollectionInterface
+    public function normalize(): BaseInterface
     {
-        return $this::with($this->run(new Normalize()));
+        return new Collection($this->run(new Normalize()));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function nth(int $step, int $offset = 0): CollectionInterface
+    public function nth(int $step, int $offset = 0): BaseInterface
     {
-        return $this::with($this->run(new Nth($step, $offset)));
+        return new Collection($this->run(new Nth($step, $offset)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function only(...$keys): CollectionInterface
+    public function only(...$keys): BaseInterface
     {
-        return $this::with($this->run(new Only($keys)));
+        return new Collection($this->run(new Only($keys)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function pad(int $size, $value): CollectionInterface
+    public function pad(int $size, $value): BaseInterface
     {
-        return $this::with($this->run(new Pad($size, $value)));
+        return new Collection($this->run(new Pad($size, $value)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function pluck($pluck, $default = null): CollectionInterface
+    public function pluck($pluck, $default = null): BaseInterface
     {
-        return $this::with($this->run(new Pluck($pluck, $default)));
+        return new Collection($this->run(new Pluck($pluck, $default)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function prepend(...$items): CollectionInterface
+    public function prepend(...$items): BaseInterface
     {
-        return $this::with($this->run(new Prepend($items)));
+        return new Collection($this->run(new Prepend($items)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
     public static function range(int $start = 0, $end = \INF, $step = 1): CollectionInterface
     {
-        return self::with((new self())->run(new Range($start, $end, $step)));
+        return new Collection((new Collection())->run(new Range($start, $end, $step)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function rebase(): CollectionInterface
+    public function rebase(): BaseInterface
     {
-        return $this::with($this->run(new Rebase()));
+        return new Collection($this->run(new Rebase()));
     }
 
     /**
@@ -395,38 +306,30 @@ public function run(Operation ...$operations)
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function skip(int ...$counts): CollectionInterface
+    public function skip(int ...$counts): BaseInterface
     {
-        return $this::with($this->run(new Skip(...$counts)));
+        return new Collection($this->run(new Skip(...$counts)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function slice(int $offset, int $length = null): CollectionInterface
+    public function slice(int $offset, int $length = null): BaseInterface
     {
-        return $this::with($this->run(new Slice($offset, $length)));
+        return new Collection($this->run(new Slice($offset, $length)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function sort(callable $callback): CollectionInterface
+    public function sort(callable $callback): BaseInterface
     {
-        return $this::with($this->run(new Sort($callback)));
+        return new Collection($this->run(new Sort($callback)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
     public static function times($number, callable $callback = null): CollectionInterface
     {
@@ -434,7 +337,7 @@ public static function times($number, callable $callback = null): CollectionInte
             return static::empty();
         }
 
-        $instance = static::with(
+        $instance = new Collection(
             static function () use ($number) {
                 for ($current = 1; $current <= $number; ++$current) {
                     yield $current;
@@ -442,38 +345,22 @@ static function () use ($number) {
             }
         );
 
-        return null === $callback ? $instance : static::with((new Run(new Walk($callback)))->on($instance));
+        return null === $callback ? $instance : new Collection((new Run(new Walk($callback)))->on($instance));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
-     */
-    public function walk(callable ...$callbacks): CollectionInterface
-    {
-        return $this::with($this->run(new Walk(...$callbacks)));
-    }
-
-    /**
-     * Create a new collection instance.
-     *
-     * @param mixed $data
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public static function with($data = []): CollectionInterface
+    public function walk(callable ...$callbacks): BaseInterface
     {
-        return new static($data);
+        return new Collection($this->run(new Walk(...$callbacks)));
     }
 
     /**
      * {@inheritdoc}
-     *
-     * @return \drupol\collection\Contract\Collection
      */
-    public function zip(...$items): CollectionInterface
+    public function zip(...$items): BaseInterface
     {
-        return $this::with($this->run(new Zip($items)));
+        return new Collection($this->run(new Zip($items)));
     }
 }
diff --git a/src/Contract/Appendable.php b/src/Contract/Appendable.php
index 62b9f3a11..906c013d5 100644
--- a/src/Contract/Appendable.php
+++ b/src/Contract/Appendable.php
@@ -14,7 +14,7 @@ interface Appendable
      *
      * @param mixed ...$items
      *
-     * @return \drupol\collection\Contract\Collection
+     * @return \drupol\collection\Contract\Base
      */
-    public function append(...$items): Collection;
+    public function append(...$items): Base;
 }
diff --git a/src/Contract/Applyable.php b/src/Contract/Applyable.php
index 0010e15b1..67dba7fe1 100644
--- a/src/Contract/Applyable.php
+++ b/src/Contract/Applyable.php
@@ -14,7 +14,7 @@ interface Applyable
      *
      * @param callable ...$callables
      *
-     * @return \drupol\collection\Contract\Collection
+     * @return \drupol\collection\Contract\Base
      */
-    public function apply(callable ...$callables): Collection;
+    public function apply(callable ...$callables): Base;
 }
diff --git a/src/Contract/Base.php b/src/Contract/Base.php
new file mode 100644
index 000000000..ef6532460
--- /dev/null
+++ b/src/Contract/Base.php
@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace drupol\collection\Contract;
+
+/**
+ * Interface Base.
+ */
+interface Base extends \IteratorAggregate
+{
+}
diff --git a/src/Contract/Chunkable.php b/src/Contract/Chunkable.php
index bda38d087..6f3adc674 100644
--- a/src/Contract/Chunkable.php
+++ b/src/Contract/Chunkable.php
@@ -14,7 +14,7 @@ interface Chunkable
      *
      * @param int $size
      *
-     * @return \drupol\collection\Contract\Collection
+     * @return \drupol\collection\Contract\Base
      */
-    public function chunk(int $size): Collection;
+    public function chunk(int $size): Base;
 }
diff --git a/src/Contract/Collapseable.php b/src/Contract/Collapseable.php
index 1dc164fbc..7f0d8ce11 100644
--- a/src/Contract/Collapseable.php
+++ b/src/Contract/Collapseable.php
@@ -14,5 +14,5 @@ interface Collapseable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function collapse(): Collection;
+    public function collapse(): Base;
 }
diff --git a/src/Contract/Collection.php b/src/Contract/Collection.php
index 21f3142d1..c5af4c42a 100644
--- a/src/Contract/Collection.php
+++ b/src/Contract/Collection.php
@@ -8,10 +8,10 @@
  * Interface Collection.
  */
 interface Collection extends
-    \IteratorAggregate,
     Allable,
     Appendable,
     Applyable,
+    Base,
     Chunkable,
     Collapseable,
     Combineable,
@@ -47,7 +47,7 @@ interface Collection extends
     /**
      * Create a new instance with no items.
      */
-    public static function empty(): self;
+    public static function empty(): Collection;
 
     /**
      * Create a new with a range of number.
diff --git a/src/Contract/Combineable.php b/src/Contract/Combineable.php
index 746777b86..1335e846e 100644
--- a/src/Contract/Combineable.php
+++ b/src/Contract/Combineable.php
@@ -14,5 +14,5 @@ interface Combineable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function combine($keys): Collection;
+    public function combine($keys): Base;
 }
diff --git a/src/Contract/Filterable.php b/src/Contract/Filterable.php
index 5c3047bb5..456c60cbb 100644
--- a/src/Contract/Filterable.php
+++ b/src/Contract/Filterable.php
@@ -16,5 +16,5 @@ interface Filterable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function filter(callable ...$callbacks): Collection;
+    public function filter(callable ...$callbacks): Base;
 }
diff --git a/src/Contract/Flattenable.php b/src/Contract/Flattenable.php
index 2e1074b77..f609dcb0d 100644
--- a/src/Contract/Flattenable.php
+++ b/src/Contract/Flattenable.php
@@ -16,5 +16,5 @@ interface Flattenable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function flatten(int $depth = \PHP_INT_MAX): Collection;
+    public function flatten(int $depth = \PHP_INT_MAX): Base;
 }
diff --git a/src/Contract/Flipable.php b/src/Contract/Flipable.php
index 6b452252d..5a1aaa24e 100644
--- a/src/Contract/Flipable.php
+++ b/src/Contract/Flipable.php
@@ -14,5 +14,5 @@ interface Flipable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function flip(): Collection;
+    public function flip(): Base;
 }
diff --git a/src/Contract/Forgetable.php b/src/Contract/Forgetable.php
index 89c082a50..000be0887 100644
--- a/src/Contract/Forgetable.php
+++ b/src/Contract/Forgetable.php
@@ -16,5 +16,5 @@ interface Forgetable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function forget(...$keys): Collection;
+    public function forget(...$keys): Base;
 }
diff --git a/src/Contract/Intersperseable.php b/src/Contract/Intersperseable.php
index 3a3fb64ff..4addf2312 100644
--- a/src/Contract/Intersperseable.php
+++ b/src/Contract/Intersperseable.php
@@ -19,5 +19,5 @@ interface Intersperseable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function intersperse($element, int $every = 1, int $startAt = 0): Collection;
+    public function intersperse($element, int $every = 1, int $startAt = 0): Base;
 }
diff --git a/src/Contract/Keysable.php b/src/Contract/Keysable.php
index 9e6dd2c48..5a574b440 100644
--- a/src/Contract/Keysable.php
+++ b/src/Contract/Keysable.php
@@ -14,5 +14,5 @@ interface Keysable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function keys(): Collection;
+    public function keys(): Base;
 }
diff --git a/src/Contract/Limitable.php b/src/Contract/Limitable.php
index 6151954df..9d199c3a3 100644
--- a/src/Contract/Limitable.php
+++ b/src/Contract/Limitable.php
@@ -16,5 +16,5 @@ interface Limitable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function limit(int $limit): Collection;
+    public function limit(int $limit): Base;
 }
diff --git a/src/Contract/Mapable.php b/src/Contract/Mapable.php
index bae2fd98c..4684266e4 100644
--- a/src/Contract/Mapable.php
+++ b/src/Contract/Mapable.php
@@ -16,5 +16,5 @@ interface Mapable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function map(callable ...$callbacks): Collection;
+    public function map(callable ...$callbacks): Base;
 }
diff --git a/src/Contract/Mergeable.php b/src/Contract/Mergeable.php
index 5ab012ddf..5e3dfbd3f 100644
--- a/src/Contract/Mergeable.php
+++ b/src/Contract/Mergeable.php
@@ -16,5 +16,5 @@ interface Mergeable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function merge(...$sources): Collection;
+    public function merge(...$sources): Base;
 }
diff --git a/src/Contract/Normalizeable.php b/src/Contract/Normalizeable.php
index 1b576bef9..68ded8d5d 100644
--- a/src/Contract/Normalizeable.php
+++ b/src/Contract/Normalizeable.php
@@ -14,5 +14,5 @@ interface Normalizeable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function normalize(): Collection;
+    public function normalize(): Base;
 }
diff --git a/src/Contract/Nthable.php b/src/Contract/Nthable.php
index e1f8db7c0..348e7264a 100644
--- a/src/Contract/Nthable.php
+++ b/src/Contract/Nthable.php
@@ -17,5 +17,5 @@ interface Nthable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function nth(int $step, int $offset = 0): Collection;
+    public function nth(int $step, int $offset = 0): Base;
 }
diff --git a/src/Contract/Onlyable.php b/src/Contract/Onlyable.php
index 83e671b6e..eaadea94b 100644
--- a/src/Contract/Onlyable.php
+++ b/src/Contract/Onlyable.php
@@ -16,5 +16,5 @@ interface Onlyable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function only(...$keys): Collection;
+    public function only(...$keys): Base;
 }
diff --git a/src/Contract/Padable.php b/src/Contract/Padable.php
index fad69e341..7a673b334 100644
--- a/src/Contract/Padable.php
+++ b/src/Contract/Padable.php
@@ -17,5 +17,5 @@ interface Padable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function pad(int $size, $value): Collection;
+    public function pad(int $size, $value): Base;
 }
diff --git a/src/Contract/Pluckable.php b/src/Contract/Pluckable.php
index a1cb7cae2..fa0de80fd 100644
--- a/src/Contract/Pluckable.php
+++ b/src/Contract/Pluckable.php
@@ -15,5 +15,5 @@ interface Pluckable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function pluck($pluck, $default = null): Collection;
+    public function pluck($pluck, $default = null): Base;
 }
diff --git a/src/Contract/Prependable.php b/src/Contract/Prependable.php
index db6c85b3f..22d38d4e7 100644
--- a/src/Contract/Prependable.php
+++ b/src/Contract/Prependable.php
@@ -16,5 +16,5 @@ interface Prependable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function prepend(...$items): Collection;
+    public function prepend(...$items): Base;
 }
diff --git a/src/Contract/Rebaseable.php b/src/Contract/Rebaseable.php
index 846112485..e4d07d196 100644
--- a/src/Contract/Rebaseable.php
+++ b/src/Contract/Rebaseable.php
@@ -12,5 +12,5 @@ interface Rebaseable
     /**
      * @return \drupol\collection\Contract\Collection
      */
-    public function rebase(): Collection;
+    public function rebase(): Base;
 }
diff --git a/src/Contract/Skipable.php b/src/Contract/Skipable.php
index ac4f2f4d9..9101d3141 100644
--- a/src/Contract/Skipable.php
+++ b/src/Contract/Skipable.php
@@ -16,5 +16,5 @@ interface Skipable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function skip(int ...$counts): Collection;
+    public function skip(int ...$counts): Base;
 }
diff --git a/src/Contract/Sliceable.php b/src/Contract/Sliceable.php
index 822428edd..86f226e45 100644
--- a/src/Contract/Sliceable.php
+++ b/src/Contract/Sliceable.php
@@ -17,5 +17,5 @@ interface Sliceable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function slice(int $offset, int $length = null): Collection;
+    public function slice(int $offset, int $length = null): Base;
 }
diff --git a/src/Contract/Sortable.php b/src/Contract/Sortable.php
index 21f82ba9e..adc52a69a 100644
--- a/src/Contract/Sortable.php
+++ b/src/Contract/Sortable.php
@@ -16,5 +16,5 @@ interface Sortable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function sort(callable $callable): Collection;
+    public function sort(callable $callable): Base;
 }
diff --git a/src/Contract/Walkable.php b/src/Contract/Walkable.php
index 0fb064fd5..d50206ae1 100644
--- a/src/Contract/Walkable.php
+++ b/src/Contract/Walkable.php
@@ -14,5 +14,5 @@ interface Walkable
      *
      * @return \drupol\collection\Contract\Collection|\drupol\collection\Contract\Collection
      */
-    public function walk(callable ...$callbacks): Collection;
+    public function walk(callable ...$callbacks): Base;
 }
diff --git a/src/Contract/Zipable.php b/src/Contract/Zipable.php
index 29fd1fd91..28efac84b 100644
--- a/src/Contract/Zipable.php
+++ b/src/Contract/Zipable.php
@@ -19,5 +19,5 @@ interface Zipable
      *
      * @return \drupol\collection\Contract\Collection
      */
-    public function zip(...$items): Collection;
+    public function zip(...$items): Base;
 }