The H 3517 casement window operator is a bronze square body type. It has a 7 in steel arm with a round disc on the tip (some older styles had a small wheel instead of a disc). The disc slides in the H 3529 casement track located on the bottom of the casement window. It is worm gear driven by a 3/8 in crank spindle. The matching crank handle that fits onto the crank spindle and installation screws are included. Mounting holes available are 3-7/8 and 4-3/4 in apart.