Measure the length of your shoe (example in image) and match it to the following chart. Measurements may vary slightly.
33 7/8" Shoe Length: Fits on 30" Wing.
39 1/16" Shoe Length: Fits on 36" Wing
46 1/8" Shoe Length: Fits on 42" Wing
52 1/8" Shoe Length: Fits on 48" Wing