Aluminum and polymer magazines for AR-15s have provided dependable service, no doubt, but if you're looking for a magazine that'll handle anything you can throw at it, then steel construction is where it's at. This AR-15 Steel Magazine is built with a body made from heat-treated carbon steel and finished with a black-oxide treatment, so even that ever-present enemy of steel, rust, is driven away, thanks to the durable construction of this mag. These USA-made Steel AR-15 Magazines are completed with the inclusion of a magazine spring made from heat-treated chrome-silicon wire, which is topped with an injection-molded magazine follower.