Our bumper plates are constructed to fit a 50mm barbell sleeve and conform with the International Weightlifting Federation norms. Our 15kg plates have a standard diameter of 450 mm. They are constructed using a steel core covered with the highest quality neoprene rubber to provide the optimal bounce when you drop the weight. The 15kg are coloured according to IWF specs as well. These plates are available individually as well as part of our Challenge Barbell Olympic Lifting Set.