This is a 30-round 5.7x28 Ruger-57 extended magazine from ProMag. Get superior firepower for your Ruger-57 pistol with the ProMag Ruger-57 5.7x28mm 30-round extended magazine. Boasting heat-treated steel construction with a corrosion-resistant black oxide finish, the Ruger 5.7 magazine is built for unmatched strength and durability in harsh and demanding conditions. Additionally, the chrome silicon wire spring and injection-molded polymer follower work together to ensure optimal cartridge alignment and reliable feeding performance with every shot.