High Performance (HP) Kiloflex black bumpers are designed improved composition to help prevent cracking and last longer. HP will perform under extreme conditions and have an increased fatigue life. They offer excellent cost performance by enhancing reliability. HP bumpers have a standard 50.4 stainless steel insert and a reliable dead bounce that can be expected from all Kiloflex bumpers. The 45lb plates have been designed to have a thinner width, allowing the athlete to load the barbell heavier.