Solid Rubber Bumper Plates made from virgin rubber not recycled rubber. Made to IWF (International Weightlifting Federation) Standard diameter 450mm (17.7165 inch). Forged Stainless Steel insert is anchored into the rubber. Low bounce, low odor, tested to 30,000 drops from a height of 9 feet without any deformation of the insert or damage to the rubber surface. For Olympic weightlifting, Crossfit, functional fitness training, commercial gyms, and home/garage gyms.