An Idler pulley is the mechanism or the shaft of a mower that presses against a serpentine belt to guide it while the mower is in operation. In addition, the idler pulleys are armed with a pre-lubricated ball bearing that protects from dirt and other debris while in operation. In order for the idler pulley to take up the extra slack from the belt, the idler pulley is built with a compression ring, which helps distribute the pulley more evenly.