I bought a used car and when I got it home both belts were just rotten and one was already broken. I needed the straps quickly and they arrived (early) the next day. It was quick to change them because they are perfect for a notched and smooth strap. I can't say how long they will last, but with the extra kit I don't think I'll ever fall with a broken belt. Make sure your machine isn't 2x as they won't work. The title is for 2 sets, NOT 2x Proheat.