The AMILA Rubber Cover A series of Olympic plates are made of cast iron, with a 70% primary rubber coating. The ring in the middle is steel for high durability and ease of changing plates on the bar. It has the feel of natural rubber, without any unpleasant odors. It is also particularly resistant to wear and does not rust. It is not dangerous for the floor, as in case of a fall or awkward placement, it will not cause damage.