Sprinco's combines advanced materials and processes - chrome silicon wire, deep cryogenic treatment and micronized moly-disulfide coating - to produce extractor springs that outperform and outlast standard components. The AR .308 Cal dual extractor CS spring upgrade kits from Sprinco USA incorporate springs made from heat-treated, cryogenically processed chrome silicon wirestock, enhanced with molybdenum disulfide plating The XP 5-coil spring provides a greater load capacity compared to OEM springs, thereby removing the necessity for D-Fender rings or CRANE viton O-rings It is compatible with all 5.56x45mm BBL lengths These springs sustain performance even under extreme duty cycles and temperatures reaching up to 750 deg F They may be the only extractor springs required for the entire lifespan of your bolt