You need two measurements. The distance ( exactly ) between the center of the two pulleys, and the diameter of the driven. It will be either 6" or 7". Looking at your picture, I'm guessing it's a 6". Then get on the Go Power Sports website, and they will have a chart that corresponds to the measurements. Then do yourself a favor and order the belt from them. You will get a much better product than the garbage sold on Amazon. Comet brand belts are the very best. But even the house brand sold by GPS is pretty good quality.