Sprinco's Extractor Springs are made of chrome silicon wirestock that has been heat treated, stress relieved, and cryogenic processing post winding. The springs are also plated with re-micronized molybdenum disulfide formulation. ADVANTAGES: XP 5-Coil spring has a heavier spring load than OEM springs, thus negating the need for a D-Fender(TM) ring or adding CRANE Viton O-Rings Use 5-Coil spring with either black extractor spring insert OR CRANE Viton O-Rings, but not both Enhanced 4-Coil springs maintain an extended duty cycle load of a NEW Mil-Spec spring and is recommended for use in 18""+BBL lengths for those who retrieve their brass for reloa Mfg: Sprinco Usa