Belt Tensioner, Industry Number, 38503Mfr #: 38503 Optimized components engineered for maximum strength and durability Patented design provides superior belt alignment and tension for improved drive efficiency and life Patented labyrinth seal prevents contamination of internal parts for maximum durability and service life Long lasting steel pulleys with dust shields to protect internal bearings from contamination Double row bearings carry more load and last up to 3X longer than two