Similar to the TITAN PROLOC™ 1 Barbell Collars, the TITAN PROLOC™ 1 Magnetic Barbell Collars contain two built-in magnets which enables easy storage by sticking them to the metal exterior of a rack upright. These made in the USA collars attach firmly and securely to any bar with a sleeve diameter ranging from 47.5mm - 50.9mm. The collars are compatible with Olympic bars and powerlifting bars as well as most logs, cambered bars, Swiss bars, and safety squat bars. Crafted from high-strength nylon that can last in the hardest gym environments for years. The PROLOC 1 features easy on/off knobs that works just as smoothly as most spring clips, but with a very secure grip.