Here's the link: http://www.noveskerifleworks.com/cgi-bin/imcart/display.cgi?cat=11 My research suggests that these work fine on mid and carbine length uppers although they were specifically designed to compliment short barreled ARs. I had intended to use it on a 13.7 inch barrel to get the overall length to 16.1, but I'm sidetracked on other stuff. This one has been mounted but is in excellent condition. Trade or partial trade for Glock 34, 17 round 9mm Glock mags, Aimpoint Comp3 or whathaveyou. If cash, 100 will do it.