Steel Bar Clamp AluminiumConsiderably stronger than the traditional spring type collars and will hold the plates in place without movement. Made with a super strong aviation grade aluminium, the inner ring is lined entirely with non slip rubber which is manufactured from moulded virgin rubber (not nylon) with zero tolerance to fit 50mm olympic barbells. Designed and used by athletes, these collars are one of the toughest in the world. The easy to use permanent snap latch