this is a Gearbox, this gearbox was totally 3D printed. You need, 2 AA battery, a 25mm motor with a 2 mm shaft, 2 steel bar of 3 mm diameter and 2 M3 screws larger than 25 mm.
When you will print the different gears you will find 2 gear that are with a smaller hole they correspond to the orange gear in the picture. Print as many gear as you want to have the speed you want. it can be really useful in your DIY creation.