Ah, so not as good as the Slap Chop.
But what was it supposed to do? It's just a piece of plastic. I guess the end of the spring snaps onto it and the diameter is large enough to wedge it in the extension tube. I think it was supposed to keep the spring from bouncing. But I don't know. I'm just scratching my head over the thinking that went into it.
I don't mind the twang, with my hearing protection on it's barely audible, so it's not something I was going to buy. I was just curious if it worked, and if so, how.