Dryer drum drive belt. The belt is flat, 92-1/4 inches long, 1/4 inch wide and has 4 ribs and 3 grooves. It replaces many other belts, including some with 5 ribs and 4 grooves. If the drum does not turn, but you can hear the motor running then there is a good chance the belt has broken.
Dryer drum drive belt, 100 inches long, 3/8" wide,5 ribs 4 grooves. The drive belt wraps all the way around the dryer drum, around a tension pulley, and then around the drive motor pulley. If the drum will not turn when the dryer is turned on the belt is likely broken.