This thing was just what I was looking for to rough up a barn's woodshed. Cuts like a chainsaw with the agility of an angle grinder. The supplied plastic center piece holds the 3 parts together. It must be removed to install on an angle grinder. This means you have to align 3 separate parts (top metal holder, bottom metal holder, middle cutting chain) on the grinder. It's not that hard, but I can see that losing one of those parts makes the whole thing useless. I wish they all rode on a center bearing or something to tie all the pieces together.