This treadmill motor drive belt is 21 inches long, or 533mm and has 8 ribs. If your motor drive belt is very worn, fitting this belt will make your treadmill a lot smoother and run a lot quieter. Like most treadmill motor drive belts it has PJ profile ribs. Check the numbers on your belt and count to number of ribs on the inside of the belt. This belt is suitable for all treadmills displaying these numbers except some Icon group treadmills (Pro Form, NordicTrack) where the numbers don’t align to international standards & where these treadmills have no motor drive belt adjustments. Some of these model may require a special drive belt.