Bolt:Type II (.136") bolt9310 Tool Steel Construction (Stronger than C158)Full MIL-SPEC Heat TreatmentShot Peened to MIL-SPECMagnetic Particle Inspection (MPI)Back of Lugs Chamfered for Reliabilityspring Insert, & "Crane" O-Ring InstalledQPQ -?Salt Bath Nitrided.136'' Co-Bore Depth "Type II" BoltExtractor:S7 Tool Steel ConstructionFully Heat TreatedShot Peened Per MIL-SPECBlack Oxide to Match Bolt?Carrier & Key:Superfinished CarrierCarrier: MIL-SPEC 8620 Steel MaterialKey: 4140 Steel MaterialFully Heat TreatedForward Assist SerrationsM16 (FULL-AUTO) CompatibleGrade 8 FastenersFully & Properly Staked Key, Permatex SealedQPQ -?Salt Bath Nitrided?Cam Pin:?4140 Pre-Hardended Steel MaterialQPQ -?Salt Bath Nitride