To assemble the parts togther, some M2 screws are needed. Parts are designed for 3d printing. It is best to use resin material when 3d printing. And you may need to sand some parts due to the 3d printing quality. You can drive the mechanism with hand, Or you can assemble a motor to make it work too. Video on Youtube: https://youtu.be/mDTnm2YQQgg
It is a digital goods, not a physical product. What you will get are STEP and STL formats files. Note: Digital goods cannot be returned. When you drive the small gear, the center hole can open or close gradually. The center hole is diameter 50mm.