CFF Rubber Bumper Plates Top quality, solid rubber bumper plates at budget-friendly prices Sold as pairs 100 percent virgin rubber Built to IWF specs 450mm diameter with a 50.4mm center collar. Built to IWF specs 450 mm (17.7165 in) diameter with 2&#034; (50.4 mm) forged stainless steel insert made from virgin (not recycled) rubber low bounce for safety tolerance: +/- 25 grams, claimed weight 25, 35, 45 lb bumpers drop tested 30,000 times from 9ft without breakage/deformation of insert or damage to rubber surface. 10, 15 lb bumpers drop tested 10,000 times from 9ft w/out breakage/deformation of insert, or damage to rubber surface.