The Dayco Serpentine Automatic Belt Tensioner for Volvo / Mack is designed to provide reliable performance and long-lasting durability. This tensioner features a thermoplastic rubber spring slot plugs and rubber O-ring seals to help keep contaminants out, a heavy duty cast aluminum spring case and arm to help resist cracking and fatigue, and zinc coated mounting bolts that resist rust. This tensioner is the perfect choice for reliable performance and long-lasting durability. FleetPride is your First Click in Heavy Duty®.