This replacement or spare magazine is compatible with your Ruger Mini Thirty. It is constructed of DuPont Zytel Polymer with injection molded mag follower & mag spring formed from heat treated chrome silicone wire. Made in the USA. Type Detachable Model Standard Finish Black Series Replacement Magazine Caliber 7.62x39mm Capacity 30 Material DuPont Zytel Polymer Brand Fit Ruger Model Fit Mini Thirty