Heavy-Duty Pulley Clutch 1/4" keyway, 4" OD pulley, One piece machined steel pulley and drum to withstand high shock loading, heavy-duty, For 3 thru 10 HP rating, Keyway: Grooved, Fits A or B belts, Upgrade from the original, For 1/2" or 5/8" section belts, 1" bore ball bearing style hub for smooth running. Fits Models: Replaces Part Numbers: Mackissic 030-0164, Troy-Bilt 1762055, Noram 160021 Stens Part Number: 255-635