Made from high-grade chrome silicon wire, Sprinco's extractor springs are heat treated, stress relieved, cryogenically processed and coated with a molybdenum disulfide formula - ensuring long-lasting strength and smooth function. The XP 5-coil extractor spring from Sprinco USA features a higher load capacity compared to OEM springs, thereby removing the necessity for supplementary rings The springs are designed to endure extreme duty cycles and temperatures up to 750 deg F the .308 Cal variant is compatible with DPMS G2 bolts for full-auto applications The upgraded 4-coil springs are designed for rifles with barrels 18 inches or longer, particularly beneficial for users who reload ammunition Conversely, the 5-coil springs provide reliable performance across all 5.56x45mm barrel lengths