As an idea it's good, no unscrewing like the others, you pass the thread, then tighten. This one you put the pieces facing each other, they wedge in, and you're okay. When you put it to tighten the screw of the trimmer, the head instead of having thickness to be able to tighten on the head of the trimmer, is more inside instead of outside to be caught by the screw, so the screw tightens and it turns on itself. Useless....