This is a smooth (flat) drive belt idler pulley for the 6.2L accessory drive. It is engineered for 6.2L V8: F-250/F-350 SD, E-350/E-450 SD (2016-2019). A failing smooth idler makes bearing noise, can wobble or seize, and contributes to belt squeal and premature belt wear; a seized pulley can shred the belt.
