The premium rubber used in our Competition Bumpers in pounds allows them to withstand 30,000 drops. They have a dead blow when dropped, with very little bounce. A larger, solid steel core creates a thinner and more durable plate, while a precise 50.3mm center hole provides a snug fit on the bar. 2 year warranty against defects. Available in pounds: 25lbs, 35lbs, 45lbs & 55lbs. Accurate to within a 1% (+ or -) weight tolerance.