ProMag Sig Sauer P320 Black 9mm Luger Handgun Magazine - 21 Rounds - This replacement or spare magazine is compatible with your Sig Sauer P320. It is constructed of heat treated steel with injection molded mag follower and mag spring formed from chrome silicone wire. Made in the USA. 21-round magazine Fits Sig Sauer P320 9mm pistol Magazine body constructed of heat treated steel with black oxide finish Injection molded magazine follower Magazine spring formed from heat treated chrome silicone wire Made in USA