This is a Fusion Firearms Pro-Series Premium, Forged 1911 colt style Precision Pro Series, Serrated Slide stop in heat treated Forged alloy Stainless steel with Brushed polished finish. For 40 Cal/10mm/9mm & 38 Super 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. The Best of the Best in 1911 performance parts, Great product for new build 1911's and rebuild projects.