DAYTON Cogged V-Belt: AX25, 27 in Outside Lg, 0.5 in Top Wd, 5/16 in Thick Product Description AX section V-belts have a classical, cogged design with a nominal top width of 1/2" and a nominal thickness of 5/16" (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.