The Zhangkong IWF Coloured Weight Plates are approved by the International Weightlifting Federation. These plates are made of steel and have a rubber coating as per IWF specifications.The diameter of the largest disc is 450mm with a tolerance of +/-1mm. The bore diameter is 50mm.There is clear indication of weight on both sides of the plates as per IWF specifications.Weights are durable and are able to withstand impact associated with Olympic lifting.Zhangkong are specialists in competition and Olympic style weightlifting equipment. All of their products are approved by the International Weightlifting Federation (IWF), meaning they meet certain specifications required for use in Olympic competition.Zhangkong equipment was used in the Beijing Olympic Games in 2008 and is built with precision and accuracy in mind. The competition style equipment is approved by the International Weightlifting Federation (IWF) for use in Olympic lifting. The training equipment, whilst not suitable for competition, is also extremely accurate in weight and dimension. The discs are all colour coded as per IWF specification. SPECIFICATION: Brand Zhangkong Usage Home Use, Commercial Use Condition Brand New Warranty 1 year warranty