The Dayco Serpentine Automatic Belt Tensioner is designed to provide reliable performance and long-lasting durability. This tensioner features zinc coated mounting bolts that resist rust, thermoplastic rubber spring slot plugs and rubber O-ring seals to help keep contaminants out, and a heavy duty cast aluminum spring case and arm to help resist cracking and fatigue. It also has a steel pivot tube on specific designs for enhanced stability and strength. FleetPride is your First Click in Heavy Duty®.