What is it for?
A gear is a rotating circular machine part having cut teeth or, in the case of a cogwheel or gearwheel, inserted teeth, which mesh with another toothed part to transmit torque and speed.
 
Specs:
Material: Metal
A = 51 mm O.D.
B = 33 mm
C = 12 mm I.D.
D = 13 mm
E = 16 mm
F = M5 – 0.8