Install these variable-speed belts in drive systems with variable-speed pulleys. They are designed to accommodate changes in speed and pulley width as the drive system slows down or speeds up. Cogs, or notches, on the inner surface of the belt allow the belt to flex easily, making these belts suitable for small-diameter pulleys. The cogs also dissipate heat, which helps prevent damage to the belt. When replacing a belt on a pulley, make sure the width of the belt is compatible with the pulley.