At OMB Warehouse, we strive to provide the greatest selection and quality of parts for your outdoor power equipment.Need other parts to complete your project? Check out our huge catalog - we have what you need.5/8" Bore Sprocket for #40/41/420 Chain 12 Tooth without Keystock5/8" Bore B Type Engine Sprocket for Jackshafts. B Type sprockets have a hub on one side. Keyways are 3/16". B sprockets have (2) 5/16-18 set screws. #40/41/420 Chain 12 Tooth No Keystock.7/8" depth of bore.