DAYTON Cogged V-Belt: BX40, 43 in Outside Lg, 0.656 in Top Wd, 13/32 in Thick Product Description BX section V-belts have a classical, cogged design with a nominal top width of 21/32" and a nominal thickness of 13/32" (actual dimensions may vary slightly). Cogged V-belts have grooves across the width of the belt and are identified with an "X." They run cooler than standard V-belts because the cogs allow the belt to bend and flex against the pulley, dissipating heat. They are useful for small diameter pulleys and drives with twists and turns. These V-belts are used in drive systems that require power transmission of 1 HP or greater. A9