It can be used with the Wall-E robot, or printed separately for other robotic locomotion mechanisms. The motor is a TT motor (it’s recommended to purchase a coaxial version; avoid the split-shaft type, as it can cause the two drive wheels to become unsynchronized and lead to chain slippage). The rotational speed is up to you. Each side has 33 track links, connected by 1-mm steel wire. You’ll also need several M3×25 mm screws with nuts for assembling the motor housing; the housing can be printed as a mirror image. For reference, see the video on Bilibili by “Meng Ye Gu Shou.”