We have 4 sizes total. The standard and most popular size is the 9/16" (medium). 1/2" is our small, 5/8" is our large and 3/4" is our xlarge. Please note that our standard disc size before June 2009 was 1/2". If you have any questions about discs sizes please contact us prior to ordering. If you own a disc already and need help with sizing your disc to match a new one, please contact us or take it to a jeweler to be measured.