This is a replacement gun magazine for Sig Sauer P220 guns. This is a .45 ACP 10 Round blue steel Promag gun magazine. Made from high quality heat treated steel and uses Du Pont impact resistant floor plate and an injection molded follower with a large finger rest sleeve for a larger grip area. This magazine features ProMag ANTI-FATIGUE LOAD’UM up and STACK’UM up chrome silicon springs. Leave you mags loaded for years without worry.