Upgrade your standard, carbon steel recoil spring, to a KVP 17-4 Stainless steel recoil spring. Carbon steel springs have the potential to rust if not properly cared for. KVP passivate finish's all our 17-4 Stainless Steel CAR recoil springs to protect them in even the harshest of environments. In addition, the Kaw Valley Precision AR-15 Carbine Spring has a cycle life rating over 10,000. If you demand the best, the KVP Carbine Spring will deliver. FeaturesUse in AR-15's (5.56, .223, 300BLK etc.)Can also be used to tune PCC's10,000 cycle ratedPassivated finishPair with a KVP 4.3oz buffer or KVP 5.4oz bufferDesigned only for Carbine Length Stock and pistol kits