All DURA-SYNC TORQUE timing belts are manufactured using the latest in synchronous belt technology. They are manufactured with a heavy duty, woven, nylon based fabric tooth covering. Timing Belt, 5M, 20 x 600mm PL, T120 D&D DURA-SYNC TORQUE belts meet or exceed USA RMA published ratings levels. They offer a dependable, economical and hassle-free alternative to chain drives.