Uesaka’s IWF approved 1 Rule kg Metal Plates are designed for quick change with our outside Sevi collar system. There are six weight increments from 0.5kg up to 5kg. With a 50.0mm diameter collar opening. These quality plates are compatible with our IWF Olympic barbell. They are color coded per IWF standards Green-Yellow-Blue-Red-White. The 2.0 kg – 0.5 kg metal plates are designed for the outside system, or can be used inside with your own collar. The 5 kg and 2.5 kg plates are inside plates only.