Garage Door Opener, Manual Chain Hoist, Max. Door Height (Ft.) 18, Standards 1 in Bore, Includes (1) Chain Keeper, (1) Wall Bracket, (2) Shaft Collars, 1/4 in Key, 22 in of #41 Roller Chain, 26 ft of Hand Chain, 4:1 Reduction, External Chain and Sprocket Drive, Jack Shaft Mounting, Sprocket