The SI Carbine Flat Wire Spring is an economical and easy upgrade to any AR system with a carbine buffer system. The flatwire spring increases service life of the platform, smooths out the shooting cycle, and greatly outlasts the stock spring Increased bolt load, in addition to decreased compression force increases reliability in cycling. Additionally, all SI Flat Wire spring are cryogenically stress relieved to provide greater consistency, longer spring life, and greater resilience to high cyclic rates. At a cost not much greater than stock carbine springs, the SI Flatwire is an easy option for those either looking to replace worn buffer spring or begin new builds. Features: Cryo-cycled 17-7 ph steel for strength, reliability and longevity Decreased harmonics lessens system vibration for faster follow up shots. Increased bolt load for more positive feeding Reduces distracting AR "twang" Specifications: OD: 0.94" ID: 0.75" Length: 13 7/8" Rev: 35 Gauge (Flat Wire Profile): 0.045" x 0.0935" Package includes: 1x Carbine Length Flat Wire Spring