diff --git a/builders/frontend_builder.py b/builders/frontend_builder.py
index c7a70725a..794f4dfe9 100644
--- a/builders/frontend_builder.py
+++ b/builders/frontend_builder.py
@@ -26,7 +26,7 @@ def build_frontend(inputs, frontend, is_training=True, pretrained_dir="models"):
         with slim.arg_scope(mobilenet_v2.training_scope()):
             logits, end_points = mobilenet_v2.mobilenet(inputs, is_training=is_training, scope='mobilenet_v2', base_only=True)
             frontend_scope='mobilenet_v2'
-            init_fn = slim.assign_from_checkpoint_fn(model_path=os.path.join(pretrained_dir, 'mobilenet_v2_1.4_224.ckpt'), var_list=slim.get_model_variables('mobilenet_v2'), ignore_missing_vars=True)
+            init_fn = slim.assign_from_checkpoint_fn(model_path=os.path.join(pretrained_dir, 'mobilenet_v2.ckpt'), var_list=slim.get_model_variables('mobilenet_v2'), ignore_missing_vars=True)
     elif frontend == 'InceptionV4':
         with slim.arg_scope(inception_v4.inception_v4_arg_scope()):
             logits, end_points = inception_v4.inception_v4(inputs, is_training=is_training, scope='inception_v4')
diff --git a/builders/model_builder.py b/builders/model_builder.py
index a99b017d0..c6e458171 100644
--- a/builders/model_builder.py
+++ b/builders/model_builder.py
@@ -45,7 +45,7 @@ def build_model(model_name, net_input, num_classes, crop_width, crop_height, fro
 	    download_checkpoints("ResNet101")
 	if "ResNet152" == frontend and not os.path.isfile("models/resnet_v2_152.ckpt"):
 	    download_checkpoints("ResNet152")
-	if "MobileNetV2" == frontend and not os.path.isfile("models/mobilenet_v2_1.4_224.ckpt.data-00000-of-00001"):
+	if "MobileNetV2" == frontend and not os.path.isfile("models/mobilenet_v2.ckpt.data-00000-of-00001"):
 	    download_checkpoints("MobileNetV2")
 	if "InceptionV4" == frontend and not os.path.isfile("models/inception_v4.ckpt"):
 	    download_checkpoints("InceptionV4") 
diff --git a/frontends/se_resnext.py b/frontends/se_resnext.py
new file mode 100644
index 000000000..938cfb561
--- /dev/null
+++ b/frontends/se_resnext.py
@@ -0,0 +1,188 @@
+import tensorflow as tf
+
+import math
+
+USE_FUSED_BN = True
+BN_EPSILON = 9.999999747378752e-06
+BN_MOMENTUM = 0.99
+
+VAR_LIST = []
+
+# input image order: BGR, range [0-255]
+# mean_value: 104, 117, 123
+# only subtract mean is used
+def constant_xavier_initializer(shape, group, dtype=tf.float32, uniform=True):
+    """Initializer function."""
+    if not dtype.is_floating:
+      raise TypeError('Cannot create initializer for non-floating point type.')
+    # Estimating fan_in and fan_out is not possible to do perfectly, but we try.
+    # This is the right thing for matrix multiply and convolutions.
+    if shape:
+      fan_in = float(shape[-2]) if len(shape) > 1 else float(shape[-1])
+      fan_out = float(shape[-1])/group
+    else:
+      fan_in = 1.0
+      fan_out = 1.0
+    for dim in shape[:-2]:
+      fan_in *= float(dim)
+      fan_out *= float(dim)
+
+    # Average number of inputs and output connections.
+    n = (fan_in + fan_out) / 2.0
+    if uniform:
+      # To get stddev = math.sqrt(factor / n) need to adjust for uniform.
+      limit = math.sqrt(3.0 * 1.0 / n)
+      return tf.random_uniform(shape, -limit, limit, dtype, seed=None)
+    else:
+      # To get stddev = math.sqrt(factor / n) need to adjust for truncated.
+      trunc_stddev = math.sqrt(1.3 * 1.0 / n)
+      return tf.truncated_normal(shape, 0.0, trunc_stddev, dtype, seed=None)
+
+# for root block, use dummy input_filters, e.g. 128 rather than 64 for the first block
+def se_bottleneck_block(inputs, input_filters, name_prefix, is_training, group, data_format='channels_last', need_reduce=True, is_root=False, reduced_scale=16):
+    bn_axis = -1 if data_format == 'channels_last' else 1
+    strides_to_use = 1
+    residuals = inputs
+    if need_reduce:
+        strides_to_use = 1 if is_root else 2
+        proj_mapping = tf.layers.conv2d(inputs, input_filters, (1, 1), use_bias=False,
+                                name=name_prefix + '_1x1_proj', strides=(strides_to_use, strides_to_use),
+                                padding='valid', data_format=data_format, activation=None,
+                                kernel_initializer=tf.contrib.layers.xavier_initializer(),
+                                bias_initializer=tf.zeros_initializer())
+        residuals = tf.layers.batch_normalization(proj_mapping, momentum=BN_MOMENTUM,
+                                name=name_prefix + '_1x1_proj/bn', axis=bn_axis,
+                                epsilon=BN_EPSILON, training=is_training, reuse=None, fused=USE_FUSED_BN)
+
+    reduced_inputs = tf.layers.conv2d(inputs, input_filters // 2, (1, 1), use_bias=False,
+                            name=name_prefix + '_1x1_reduce', strides=(1, 1),
+                            padding='valid', data_format=data_format, activation=None,
+                            kernel_initializer=tf.contrib.layers.xavier_initializer(),
+                            bias_initializer=tf.zeros_initializer())
+    reduced_inputs_bn = tf.layers.batch_normalization(reduced_inputs, momentum=BN_MOMENTUM,
+                                        name=name_prefix + '_1x1_reduce/bn', axis=bn_axis,
+                                        epsilon=BN_EPSILON, training=is_training, reuse=None, fused=USE_FUSED_BN)
+    reduced_inputs_relu = tf.nn.relu(reduced_inputs_bn, name=name_prefix + '_1x1_reduce/relu')
+
+    if data_format == 'channels_first':
+        reduced_inputs_relu = tf.pad(reduced_inputs_relu, paddings = [[0, 0], [0, 0], [1, 1], [1, 1]])
+        weight_shape = [3, 3, reduced_inputs_relu.get_shape().as_list()[1]//group, input_filters // 2]
+        weight_ = tf.Variable(constant_xavier_initializer(weight_shape, group=group, dtype=tf.float32), trainable=is_training, name=name_prefix + '_3x3/kernel')
+        weight_groups = tf.split(weight_, num_or_size_splits=group, axis=-1, name=name_prefix + '_weight_split')
+        xs = tf.split(reduced_inputs_relu, num_or_size_splits=group, axis=1, name=name_prefix + '_inputs_split')
+    else:
+        reduced_inputs_relu = tf.pad(reduced_inputs_relu, paddings = [[0, 0], [1, 1], [1, 1], [0, 0]])
+        weight_shape = [3, 3, reduced_inputs_relu.get_shape().as_list()[-1]//group, input_filters // 2]
+        weight_ = tf.Variable(constant_xavier_initializer(weight_shape, group=group, dtype=tf.float32), trainable=is_training, name=name_prefix + '_3x3/kernel')
+        weight_groups = tf.split(weight_, num_or_size_splits=group, axis=-1, name=name_prefix + '_weight_split')
+        xs = tf.split(reduced_inputs_relu, num_or_size_splits=group, axis=-1, name=name_prefix + '_inputs_split')
+
+    convolved = [tf.nn.convolution(x, weight, padding='VALID', strides=[strides_to_use, strides_to_use], name=name_prefix + '_group_conv',
+                    data_format=('NCHW' if data_format == 'channels_first' else 'NHWC')) for (x, weight) in zip(xs, weight_groups)]
+
+    if data_format == 'channels_first':
+        conv3_inputs = tf.concat(convolved, axis=1, name=name_prefix + '_concat')
+    else:
+        conv3_inputs = tf.concat(convolved, axis=-1, name=name_prefix + '_concat')
+
+    conv3_inputs_bn = tf.layers.batch_normalization(conv3_inputs, momentum=BN_MOMENTUM, name=name_prefix + '_3x3/bn',
+                                        axis=bn_axis, epsilon=BN_EPSILON, training=is_training, reuse=None, fused=USE_FUSED_BN)
+    conv3_inputs_relu = tf.nn.relu(conv3_inputs_bn, name=name_prefix + '_3x3/relu')
+
+
+    increase_inputs = tf.layers.conv2d(conv3_inputs_relu, input_filters, (1, 1), use_bias=False,
+                                name=name_prefix + '_1x1_increase', strides=(1, 1),
+                                padding='valid', data_format=data_format, activation=None,
+                                kernel_initializer=tf.contrib.layers.xavier_initializer(),
+                                bias_initializer=tf.zeros_initializer())
+    increase_inputs_bn = tf.layers.batch_normalization(increase_inputs, momentum=BN_MOMENTUM,
+                                        name=name_prefix + '_1x1_increase/bn', axis=bn_axis,
+                                        epsilon=BN_EPSILON, training=is_training, reuse=None, fused=USE_FUSED_BN)
+
+    if data_format == 'channels_first':
+        pooled_inputs = tf.reduce_mean(increase_inputs_bn, [2, 3], name=name_prefix + '_global_pool', keep_dims=True)
+    else:
+        pooled_inputs = tf.reduce_mean(increase_inputs_bn, [1, 2], name=name_prefix + '_global_pool', keep_dims=True)
+
+    down_inputs = tf.layers.conv2d(pooled_inputs, input_filters // reduced_scale, (1, 1), use_bias=True,
+                                name=name_prefix + '_1x1_down', strides=(1, 1),
+                                padding='valid', data_format=data_format, activation=None,
+                                kernel_initializer=tf.contrib.layers.xavier_initializer(),
+                                bias_initializer=tf.zeros_initializer())
+    down_inputs_relu = tf.nn.relu(down_inputs, name=name_prefix + '_1x1_down/relu')
+
+    up_inputs = tf.layers.conv2d(down_inputs_relu, input_filters, (1, 1), use_bias=True,
+                                name=name_prefix + '_1x1_up', strides=(1, 1),
+                                padding='valid', data_format=data_format, activation=None,
+                                kernel_initializer=tf.contrib.layers.xavier_initializer(),
+                                bias_initializer=tf.zeros_initializer())
+    prob_outputs = tf.nn.sigmoid(up_inputs, name=name_prefix + '_prob')
+
+    rescaled_feat = tf.multiply(prob_outputs, increase_inputs_bn, name=name_prefix + '_mul')
+    pre_act = tf.add(residuals, rescaled_feat, name=name_prefix + '_add')
+    return tf.nn.relu(pre_act, name=name_prefix + '/relu')
+    #return tf.nn.relu(residuals + prob_outputs * increase_inputs_bn, name=name_prefix + '/relu')
+
+def se_resnext(input_image, scope, is_training = False, group=16, data_format='channels_last', net_depth=50):
+    end_points = dict()
+
+    bn_axis = -1 if data_format == 'channels_last' else 1
+    # the input image should in BGR order, note that this is not the common case in Tensorflow
+    # convert from RGB to BGR
+    if data_format == 'channels_last':
+        image_channels = tf.unstack(input_image, axis=-1)
+        swaped_input_image = tf.stack([image_channels[2], image_channels[1], image_channels[0]], axis=-1)
+    else:
+        image_channels = tf.unstack(input_image, axis=1)
+        swaped_input_image = tf.stack([image_channels[2], image_channels[1], image_channels[0]], axis=1)
+    #swaped_input_image = input_image
+
+    if net_depth not in [50, 101]:
+        raise TypeError('Only ResNeXt50 or ResNeXt101 are currently supported.')
+    input_depth = [256, 512, 1024, 2048] # the input depth of the the first block is dummy input
+    num_units = [3, 4, 6, 3] if net_depth==50 else [3, 4, 23, 3]
+
+    block_name_prefix = ['conv2_{}', 'conv3_{}', 'conv4_{}', 'conv5_{}']
+
+    if data_format == 'channels_first':
+        swaped_input_image = tf.pad(swaped_input_image, paddings = [[0, 0], [0, 0], [3, 3], [3, 3]])
+    else:
+        swaped_input_image = tf.pad(swaped_input_image, paddings = [[0, 0], [3, 3], [3, 3], [0, 0]])
+
+    inputs_features = tf.layers.conv2d(swaped_input_image, input_depth[0]//4, (7, 7), use_bias=False,
+                                name='conv1/7x7_s2', strides=(2, 2),
+                                padding='valid', data_format=data_format, activation=None,
+                                kernel_initializer=tf.contrib.layers.xavier_initializer(),
+                                bias_initializer=tf.zeros_initializer())
+    VAR_LIST.append('conv1/7x7_s2')
+
+    inputs_features = tf.layers.batch_normalization(inputs_features, momentum=BN_MOMENTUM,
+                                        name='conv1/7x7_s2/bn', axis=bn_axis,
+                                        epsilon=BN_EPSILON, training=is_training, reuse=None, fused=USE_FUSED_BN)
+    inputs_features = tf.nn.relu(inputs_features, name='conv1/relu_7x7_s2')
+
+    inputs_features = tf.layers.max_pooling2d(inputs_features, [3, 3], [2, 2], padding='same', data_format=data_format, name='pool1/3x3_s2')
+
+    is_root = True
+    for ind, num_unit in enumerate(num_units):
+        need_reduce = True
+        for unit_index in range(1, num_unit+1):
+            inputs_features = se_bottleneck_block(inputs_features, input_depth[ind], block_name_prefix[ind].format(unit_index), is_training=is_training, group=group, data_format=data_format, need_reduce=need_reduce, is_root=is_root)
+            need_reduce = False
+        end_points['pool' + str(ind)] = inputs_features
+        is_root = False
+
+    if data_format == 'channels_first':
+        pooled_inputs = tf.reduce_mean(inputs_features, [2, 3], name='pool5/7x7_s1', keep_dims=True)
+    else:
+        pooled_inputs = tf.reduce_mean(inputs_features, [1, 2], name='pool5/7x7_s1', keep_dims=True)
+
+    pooled_inputs = tf.layers.flatten(pooled_inputs)
+
+    # logits_output = tf.layers.dense(pooled_inputs, num_classes,
+    #                             kernel_initializer=tf.contrib.layers.xavier_initializer(),
+    #                             bias_initializer=tf.zeros_initializer(), use_bias=True)
+
+    logits_output = None
+
+    return logits_output, end_points, VAR_LIST
diff --git a/utils/get_pretrained_checkpoints.py b/utils/get_pretrained_checkpoints.py
index 9435267d2..b11af4727 100644
--- a/utils/get_pretrained_checkpoints.py
+++ b/utils/get_pretrained_checkpoints.py
@@ -7,127 +7,30 @@
 parser.add_argument('--model', type=str, default="ALL", help='Which model weights to download')
 args = parser.parse_args()
 
-###############################
-# VGG Net
-###############################
-# subprocess.check_output(['wget','http://download.tensorflow.org/models/vgg_16_2016_08_28.tar.gz'])
-# subprocess.check_output(['tar', '-xvf', 'vgg_16_2016_08_28.tar.gz'])
-# subprocess.check_output(['mv', 'vgg_16.ckpt', 'models'])
-# subprocess.check_output(['rm', 'vgg_16_2016_08_28.tar.gz'])
 
-# subprocess.check_output(['wget','http://download.tensorflow.org/models/vgg_19_2016_08_28.tar.gz'])
-# subprocess.check_output(['tar', '-xvf', 'vgg_19_2016_08_28.tar.gz'])
-# subprocess.check_output(['mv', 'vgg_19.ckpt', 'models'])
-# subprocess.check_output(['rm', 'vgg_19_2016_08_28.tar.gz'])
-
-###############################
-# Inception Net
-###############################
-# subprocess.check_output(['wget','http://download.tensorflow.org/models/inception_v1_2016_08_28.tar.gz'])
-# subprocess.check_output(['tar', '-xvf', 'inception_v1_2016_08_28.tar.gz'])
-# subprocess.check_output(['mv', 'inception_v1.ckpt', 'models'])
-# subprocess.check_output(['rm', 'inception_v1_2016_08_28.tar.gz'])
-
-# subprocess.check_output(['wget','http://download.tensorflow.org/models/inception_v2_2016_08_28.tar.gz'])
-# subprocess.check_output(['tar', '-xvf', 'inception_v2_2016_08_28.tar.gz'])
-# subprocess.check_output(['mv', 'inception_v2.ckpt', 'models'])
-# subprocess.check_output(['rm', 'inception_v2_2016_08_28.tar.gz'])
-
-# subprocess.check_output(['wget','http://download.tensorflow.org/models/inception_v3_2016_08_28.tar.gz'])
-# subprocess.check_output(['tar', '-xvf', 'inception_v3_2016_08_28.tar.gz'])
-# subprocess.check_output(['mv', 'inception_v3.ckpt', 'models'])
-# subprocess.check_output(['rm', 'inception_v3_2016_08_28.tar.gz'])
-
-# subprocess.check_output(['wget','http://download.tensorflow.org/models/inception_v4_2016_09_09.tar.gz'])
-# subprocess.check_output(['tar', '-xvf', 'inception_v4_2016_09_09.tar.gz'])
-# subprocess.check_output(['mv', 'inception_v4.ckpt', 'models'])
-# subprocess.check_output(['rm', 'inception_v4_2016_09_09.tar.gz'])
-
-# subprocess.check_output(['wget','http://download.tensorflow.org/models/inception_resnet_v2_2016_08_30.tar.gz'])
-# subprocess.check_output(['tar', '-xvf', 'inception_resnet_v2_2016_08_30.tar.gz'])
-# subprocess.check_output(['mv', 'inception_resnet_v2.ckpt', 'models'])
-# subprocess.check_output(['rm', 'inception_resnet_v2_2016_08_30.tar.gz'])
-
-
-###############################
-# ResNet V1
-###############################
-# subprocess.check_output(['wget','http://download.tensorflow.org/models/resnet_v1_50_2016_08_28.tar.gz'])
-# subprocess.check_output(['tar', '-xvf', 'resnet_v1_50_2016_08_28.tar.gz'])
-# subprocess.check_output(['mv', 'resnet_v1_50.ckpt', 'models'])
-# subprocess.check_output(['rm', 'resnet_v1_50_2016_08_28.tar.gz'])
-
-# subprocess.check_output(['wget','http://download.tensorflow.org/models/resnet_v1_101_2016_08_28.tar.gz'])
-# subprocess.check_output(['tar', '-xvf', 'resnet_v1_101_2016_08_28.tar.gz'])
-# subprocess.check_output(['mv', 'resnet_v1_101.ckpt', 'models'])
-# subprocess.check_output(['rm', 'resnet_v1_101_2016_08_28.tar.gz'])
-
-# subprocess.check_output(['wget','http://download.tensorflow.org/models/resnet_v1_152_2016_08_28.tar.gz'])
-# subprocess.check_output(['tar', '-xvf', 'resnet_v1_152_2016_08_28.tar.gz'])
-# subprocess.check_output(['mv', 'resnet_v1_152.ckpt', 'models'])
-# subprocess.check_output(['rm', 'resnet_v1_152_2016_08_28.tar.gz'])
-
-
-###############################
-# ResNet V2
-###############################
 if args.model == "ResNet50" or args.model == "ALL":
-	subprocess.check_output(['wget','http://download.tensorflow.org/models/resnet_v2_50_2017_04_14.tar.gz', "-P", "models"])
-	try:
-		subprocess.check_output(['tar', '-xvf', 'models/resnet_v2_50_2017_04_14.tar.gz', "-C", "models"])
-		subprocess.check_output(['rm', 'models/resnet_v2_50_2017_04_14.tar.gz'])
-	except Exception as e:
-		print(e)
-		pass
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/resnet_v2_50.ckpt', "-P", "models"])
 
 if args.model == "ResNet101" or args.model == "ALL":
-	subprocess.check_output(['wget','http://download.tensorflow.org/models/resnet_v2_101_2017_04_14.tar.gz', "-P", "models"])
-	try:
-		subprocess.check_output(['tar', '-xvf', 'models/resnet_v2_101_2017_04_14.tar.gz', "-C", "models"])
-		subprocess.check_output(['rm', 'models/resnet_v2_101_2017_04_14.tar.gz'])
-	except Exception as e:
-		print(e)
-		pass
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/resnet_v2_101.ckpt', "-P", "models"])
 
 if args.model == "ResNet152" or args.model == "ALL":
-	subprocess.check_output(['wget','http://download.tensorflow.org/models/resnet_v2_152_2017_04_14.tar.gz', "-P", "models"])
-	try:
-		subprocess.check_output(['tar', '-xvf', 'models/resnet_v2_152_2017_04_14.tar.gz', "-C", "models"])
-		subprocess.check_output(['rm', 'models/resnet_v2_152_2017_04_14.tar.gz'])
-	except Exception as e:
-		print(e)
-		pass
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/resnet_v2_152.ckpt', "-P", "models"])
 
 if args.model == "MobileNetV2" or args.model == "ALL":
-	subprocess.check_output(['wget','https://storage.googleapis.com/mobilenet_v2/checkpoints/mobilenet_v2_1.4_224.tgz', "-P", "models"])
-	try:
-		subprocess.check_output(['tar', '-xvf', 'models/mobilenet_v2_1.4_224.tgz', "-C", "models"])
-		subprocess.check_output(['rm', 'models/mobilenet_v2_1.4_224.tgz'])
-	except Exception as e:
-		print(e)
-		pass
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/mobilenet_v2.ckpt.meta', "-P", "models"])
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/mobilenet_v2.ckpt.index', "-P", "models"])
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/mobilenet_v2.ckpt.data-00000-of-00001', "-P", "models"])
 
 if args.model == "InceptionV4" or args.model == "ALL":
-	subprocess.check_output(['wget','http://download.tensorflow.org/models/inception_v4_2016_09_09.tar.gz', "-P", "models"])
-	try:
-		subprocess.check_output(['tar', '-xvf', 'inception_v4_2016_09_09.tar.gz', "-C", "models"])
-		subprocess.check_output(['rm', 'inception_v4_2016_09_09.tar.gz'])
-	except Exception as e:
-		print(e)
-		pass
-
-if args.model == "NASNet" or args.model == "ALL":
-	subprocess.check_output(['wget','https://storage.googleapis.com/download.tensorflow.org/models/nasnet-a_large_04_10_2017.tar.gz', "-P", "models"])
-	try:
-		subprocess.check_output(['tar', '-xvf', 'nasnet-a_large_04_10_2017.tar.gz', "-C", "models"])
-		subprocess.check_output(['rm', 'nasnet-a_large_04_10_2017.tar.gz'])
-	except Exception as e:
-		print(e)
-		pass
-
-try:
-	subprocess.check_output(['rm', 'train.graph'])
-	subprocess.check_output(['rm', 'eval.graph'])
-except Exception as e:
-		print(e)
-		pass
\ No newline at end of file
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/inception_v4.ckpt', "-P", "models"])
+	
+if args.model == "SEResNeXt50" or args.model == "ALL":
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/se_resnext50.ckpt.meta', "-P", "models"])
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/se_resnext50.ckpt.index', "-P", "models"])
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/se_resnext50.ckpt.data-00000-of-00001', "-P", "models"])
+
+if args.model == "SEResNeXt101" or args.model == "ALL":
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/se_resnext101.ckpt.meta', "-P", "models"])
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/se_resnext101.ckpt.index', "-P", "models"])
+	subprocess.check_output(['wget','https://s3.amazonaws.com/pretrained-weights/se_resnext101.ckpt.data-00000-of-00001', "-P", "models"])