Coupling & Gears,  a coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end movement or both.

Coupling & Gears , MK8 stainless steel Extruder Drive Gear, although being very small in size, is an important part of an extruder system. It is the part that fits onto the shaft of NEMA 17 Stepper Motors to grip the filament and push it towards the hot-end