ACDelco 4K378 Professional V-Ribbed Serpentine Belt Made with temperature and crack resistant EPDM rubber for a long life and quiet, dependable performance Is the belt of choice by professional technicians, lasting 50% to 60% longer than retail belts (low priced belts sold at car part stores) Its precision dimension control of rib profile transmits load efficiently throughout the accessory belt drive systems (ABDS) allowing components to operate at optimum levels Able to operate and accept misalignment in the accessory belt drive systems (ABDS) far greater than other serpentine belts Its flexible construction allows the belt to withstand billions of topside and backside bends resulting in a long belt life