The file 'HOWARD 12V Nema 17 Stepper Wheel 3D Printer Model' is (123dx,stl) file type, size is 109.2KB.
This is a wheel designed to fit on the stepper motor linked below. A rubber band fits nicely around the circumference to provide traction.
http://www.pollin.de/shop/dt/NTQ2OTg2OTk-/Motoren/Schrittmotoren/Schrittmotor_HOWARD_IND_1_19_4201.html