DAYCO NO SLACK TENSIONER PULLEY -- 81 mm OD, 17 mm ID, 13 mm W; Constructed of specially formulated glass-filled polymers for high-strength, cooler running and maximum wear resistance; Use of state-of-the-art 3-D computer aided design and finite element analysis guarantees optimal design and maximum structural integrity; Engineered with smoother surfaces and tighter dimensional tolerances for lesser vibration extending the belt's life; Lifetime lubricated ball bearings and double high temperature seals assure peak bearing performance.