Gear Kit for all chain or chain & cable combination Liftmaster, Chamberlain, and Sears openers made from 1984 to current. Contains Drive Shaft, Drive Gear, Worm Gear, Washers, Bearings, E-ring, C-ring, Collar, diagram and instructions. For reference, the diameter of the Drive Gear, shown bleach white, is 2-3/4 inches.  For belt drive units use 41A2817 gear kit.