The Comet 5005.0221.00 Gear Reducer is designed for directly mounting to a gas engine with a 1" shaft.
The Comet Gear Reduction will work with the following Comet Diaphragm Pumps: Comet APS51, APS71, and APS96.
You also need to ensure the Comet Gear Reducer is compatible with certain gas engines and meets horsepower requirements. It will work on the following brand name engines: Briggs (8 HP); Vanguard (9, 11, 13 HP); Honda (8, 9, 11, 13 HP); and Kohler Command (11, 14 HP).