diff --git a/book/opmanual_duckiebot/atoms_17_setup_duckiebot_DB17-jwd/1_0_21_assembling_duckiebot_DB18.md b/book/opmanual_duckiebot/atoms_17_setup_duckiebot_DB17-jwd/1_0_21_assembling_duckiebot_DB18.md
index 5ebc987..f3155b5 100644
--- a/book/opmanual_duckiebot/atoms_17_setup_duckiebot_DB17-jwd/1_0_21_assembling_duckiebot_DB18.md
+++ b/book/opmanual_duckiebot/atoms_17_setup_duckiebot_DB17-jwd/1_0_21_assembling_duckiebot_DB18.md
@@ -142,7 +142,7 @@ From the Duckiebox package take the following components:
 
 - Steel omni-directional wheel (1x)
 - M3x25 metal spacers (2x)
-- M3x10 screws (2x)
+- M3x10 (or M3x8) screws (2x)
 
 
 [](#fig:howto-mount-omniwheel-parts-db18) shows the components needed to complete this part of the tutorial.
@@ -151,9 +151,6 @@ From the Duckiebox package take the following components:
      <img src="howto_mount_omniwheel_parts-db18.jpg" style='width: 25em'/>
 </div>
 
-
-
-
 ### Step 1
 
 Secure the M3x25 spacers to the omni-directional wheel using *2* M3 screws (M6 to M10 will work, choose the shortest you have in your pack) as shown in [](#fig:howto-mount-omniwheel).
@@ -464,7 +461,7 @@ From the previously prepared pieces take the following components:
 From the Duckiebot kit take the following components:
 
 - M2.5x10 Nylon screws (4x)
-- M2.5x10 Nylon spacers (4x)
+- M2.5x4 Nylon spacers (4x)
 
 [](#fig:howto-assemble-rpi-top-parts) shows the components needed to complete this part of the tutorial.
 
@@ -751,14 +748,11 @@ Insert and fasten the screws trough the top plate in the front chassis spacers.
 
 ## Back bumper assembly {#howto-mount-back-bumper}
 
-From the previously prepared pieces take the following components:
+From the previously prepared assemblies, and from the Duckiebox, take the following components:
 
 - Assembled chassis (1x)
 - Back bumper assembly (1x)
-
-From the Duckiebot kit take the following components:
-
-- M3x10 screws (1x)
+- (sometimes, if you are unlucky, M3 screw (1x) and nut. You shouldn't need it.)
 
 [](#fig:howto-mount-back-bumper-parts) shows the components needed to complete this upgrade.