Look out for the three mile island hubs, tapered in the center ,thicker at the spokes .You'll really need a set of calipers to measure it correctly .Take several measurements across the hub. It should measure the same all the way across within a couple of thousands.Once you have the correct size order it and never look back. It is by far the best bolt on you can buy for your bike. I would even buy another set of wheels if i had to. Oh yea i did buy another set of wheels.