I don''t know if they expect it to fit only a NB shoe or something (mine''s Asics), but mine fell off the first time I used it this morning. I had to back track to find it. It doesn''t have enough contact and friction to stay on the rear of the shoe when you are pounding down the road. I guess you could wear it around your ankle. I wore it just above the elbow for the remainder of the morning run. In either case you will also have to tolerate the pinching pressure on you body.