The Proloc 1 Magnet Collars contain magnets inside the collar for easy storage of the collars when not in use. The PROLOC 1 Collar is made from high strength nylon. These collars fIt any bar with a diameter ranging from 1.937" to 2.007" (Fits most bars, Fits all olympic bars) Compatible with Olympic bars and Powerlifting bars as well as most logs, cambered bars, Swiss bars, and safety squat yoke bars. Sold in sets of TWO. The strength and durability of these collars can last in the hardest gym environments for years.