Bodymax Olympic Rubber Radial Weight Plates are designed to make lifting and loading weights onto bars easier. The rubber coating provides a more aesthetic finish than plain or painted cast iron finishes. The rubber coating also protects against rust and reduces noise of discs clanking against each other - rubber also protects floor coverings. All disc sizes are available in black, additionally larger disc sizes are available in colour coded options: 10kg (green), 15kg (yellow) , 20kg (blue) and 25kg (red). This product is categorised as an Olympic format weight lifting product - each end of an Olympic bar is 50mm (2 inches) diameter, and olympic weights have a hole in the centre of each disc of just over 50mm (2 inches) diameter that enable it to be used on Olympic bars. In the UK, the other main format of weight lifting bar and weights is categorised as Standard - standard bars are 25.4mm (1 inch) thick, and Standard weights have a hole in the centre of each disc of just over 25.4mm (1 inch) thick enabling them to be used on Standard bars. Be careful to order the correct gauge of bar or weights.