This is a Fusion Firearms Pro-Series 1911 colt style Precision Pro Series, Serrated Slide stop in heat treated alloy Stainless steel, Brushed polished finished. For 45 Acp Caliber pistols Precision machined from Bar Stock. This is a very high quality part, No-MIM. .1995 - .2005" diameter shaft to help aid in precision lock-up. Great product for new build 1911's and rebuild projects.