Two of these belts failed within 1 mile when used at < 18mph. The instructions are 4 sentences long and only say "put on" but not how much. I tightened it up enough that the straps didn't move. One of the straps slipped and the tensioner got crushed (good thing I have a utility knife), the other just came loose and half the device hit the wheel arch. These things took about 30 minutes to put on and broke after 3 minutes.