The drive horns go through both sides of the gearbox. The potentiometer is mounted to the gearbox indirectly using an involute gear. UPDATE: Use the -1 files. They are newer and make screwing the gearbox together easier.Requires: All parts can be printed at 0.3mm EXCEPT the gearboxscrew.stl 1) print 2) assemble slice gearboxscrew.stl at 0.2mm or less. Print very slowly with a fan as this has lots of steep angles Servo modification: You will need to take the servo apart and modify it to allow continuous rotation Assembly: All parts should go togther as per the exploded diagram. Once assembled, push the potentiometer through the hole in part "bottom plate pot holder" attach with a screw Special Mention: Although this gearbox was designed independatly of hairygael's "inmoov" gearbox design, there was a heavy dose of inspiration from the "inmoov" design. Once I saw that design, mine chaged slightly.