Had it for years, great upper - Stag Arms Right Handed Upper Receiver w/ Flash Hider

I bought this upper in 2009 or 2010 and put it on a rock river lower w/ DPMS innards. This upper has worked great ever since. I have it zeroed for 200 and it is a tack driver with 55gr. cheap American Eagle FMJ ammo and I have never had to change the zero on the scope since I first set it up years ago. It will not tolerate steel cased ammo though (neither will most ARs). The casing will get stuck in the chamber and the extractor will rip part of the rim off the casing. As far as the rate of twist mentioned in another review, I have not measured it myself, but the results with cheap ammo are good enough for me. Is it more expensive than other complete uppers, yes, but you get good quality with this one. I have a couple cheaper ones and there is a noticeable difference in part quality and assembly quality. I love mine.