Doesn't fit all 1911's apparently - Ed Brown Products Pistol Magazine, 1911 10mm, 8-Round

I bought this mag almost 2 years ago and took it out for the first time a couple weeks ago. It will not fit in my Rock Island 10mm 1911 unless the slide is locked back, at which point the slide will not go forward because the mag sticks up too high into the chamber. Other than that, it seems like it is a well build mag.