Doesnt fit - XTS Extended Bolt Assisted Releases

So i purchased this seeing that it was a pretty decent price. So once received i tried it on my dpms lower first it didnt work so, i grab my AERO built Ar same problem, so i then decided to check if i was just tripping or was this not fitting at all. So i pulled from one of my other rifles a different companys extended bolt catch and tried to put this one on it same issue"NO GO" � highly dont recommend. Just spend a lil more and get something reliable.