The size of the wheels is important if you want a full fender set. If the diameter of the fender is the same as your wheel, you may experience friction against the wheel. Similarly, if the fender is too huge, the water will spray around, making you wet. There are a few options that are adjustable to fit the wheels perfectly with different diameters. Otherwise, measure the diameter of your wheels and then find a fender set that fits that particular diameter.