ACDelco GM Original Equipment Drive Belt Idler Pulleys are part of the accessory drive belt system on the front of your engine and are GM-recommended replacements for your vehicle's original components. A pulley can be ribbed or smooth and contains a sealed ball-bearing. The idler pulley is used to divert the drive belt to components such as the alternator, water pump or power steering pump. This original equipment drive belt idler pulley has been manufactured to fit your GM vehicle, providing the same performance, durability, and service life you expect from General Motors.