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 = 37 mm O.D.
B = 22 mm
C = 12 mm I.D.
D = 17 mm
E = 22 mm
F = 4 mm Opening
G = M6 – 1.0