The SI Carbine Flat Wire Spring is an affordable and simple upgrade for any AR system with a carbine buffer. The Flat Wire spring extends the service life of the platform, smooths the shooting cycle, and significantly outlasts the stock spring. Increased bolt load, along with decreased compression force, enhances cycling reliability. Additionally, all SI Flat Wire springs are cryogenically stress-relieved to ensure greater consistency, longer spring life, and better resilience to high cyclic rates. At a cost similar to stock carbine springs, the SI Flat Wire is a convenient choice for those replacing worn buffer springs or building new rifles.