I have an AR10 receiver that someone tried to modify by grinding the rear mounting lug more narrow. Dont ask why??? I didn't want to throw it away, because I'm sure there are people out that could machine it and fix it properly. These are getting hard to find and expensive ($180). It fit fine in my lower, but there was some slop. The front pin is tight. Other than the rear mounting pin, it's like new. Call or text 8O188552OO