A compact design that locates the grub screw inside of the teeth area, enabling this printer to be possible.

KB3D sales a version of this pulley that separates the grub screw and teeth areas. This makes the pulley teeth mesh perfectly throughout the whole revolution. This is a nice design, but the AliExpress version works fine. You can buy 2 of the pulleys from KB3D for the 3mm belt. The AliExpress ones are required for the Z-Axis.