Product Description Product Info for Alpha Tactical AR-10 Chrome Car Stock Spring, .308 Cal CAR/M4 Size For AR-15 .556 Cal Teflon Coated Smoother Cycling And Alot More Quiet Fits Mil-spec/Commercial Buffer Tubes Specifications for Alpha Tactical AR-10 Chrome Car Stock Spring, .556 Cal: Color: Silver or Black Fabric/Material: Chrome Gun Model: AR-15 Package Contents: Alpha Tactial AR-15 Black or Chrome Stock Spring, .556 Cal