Promag AR-15 .223 Cal 10 Round Blue Steel Magazine. A 10-rd Magazine for AR-15 rifles chambered in .223cal/5.56x45mm, with the body of the G.I. 20-rd magazine. Magazine body constructed of heat treated steel with a black oxide finish for durability and harsh use in the field. A Chrome-silicon wire spring and precision molded polymer follower ensure reliable feeding and function.