Flat wire 30-Round Magazine Springs from Sprinco! Store Your Shtf Go-To Mags Indefinitely To Full Capacity Without Spring Fatigue! Springs Cannot Be Over-Compressed Using Anti-Tilt Followers Improved Follower Support To Top 4 Rounds, But Easier To Load To Full Capacity Springs Do Not Buckle Like Round Wire Springs, Assuring Uniform Feed Rate Fits Most Mag Bodies And Anti-Tilt Followers Including USGI, Magpul, Lancer, Hexmag, Orlite, With Few Exceptions Exceptions - Brownells USGI Tan Followers, ETS Mags, Some HK Followers 17-7 Stainless Mil-Spec Wire Construction Mfg: Sprinco Usa