Often we are asked by a potential buyer that if my existing weight plates purchased from else where are compatible with Muscle Motion standard barbell. There are 25mm and 28mm on the market, both are called standard size. If your plates are ancient, purchased from Rebel Sports, likely they are 25mm. Our standard bar is 28mm, 90% of other sellers are 28mm too. Simple tip is drop a 20 cents Australian coin into the bore hole of your plates, if just fit perfectly (not too easy means your plates are 25mm) means our barbell is going to be compatible. www.gymdirect.com.au or call 1300 488 866