Kit includes: Qty 3 - BCM Extractor Spring (chrome silicon, heat treated & stress relieved, shot peened) Qty 3 - Crane Ind O-Ring (Mil-Spec) Qty 3 - Black Extractor Insert The BCM Extractor Spring is a heavy coil design made for the increased extractor tension required on many AR15, M4, M16 short barreled rifles. This product also improves the reliability on a standard 16&';&'; and 14.5&';&'; carbines.table.productattributes, .productattributes td { border-bottom: 1px solid #ddd; border-collapse: collapse; padding: 2px; text-align: left; }