The Battle Arms Enhanced Bolt Catch offers Enhanced Control Surfaces, Better Ergonomics, Lightweight Engineering. Manufactured from Strong Billet 8620 Heat Treated Steel, the Enhanced bolt catch is Precision CNC Machined. The Versatile Modular Design allows for Future Add-On Product/s. FeaturesPrecision CNC Billet 8620 Heat Treated Steel (not cast or MIM)Oversize Control Surfaces for Easy EngagementLightweight but Robust DesignRaised "T-Shaped" Heel Provides Positive and Distinctive Control Surface for Bolt Lock BackCompatible with Norgon Ambi-Catch Without InterferenceElegant Tapered Control Surface and Skeletonized DesignBold Horizontal and Diagonal Serrations Provides Positive Purchase Note: Last round hold open will not work with dedicated Colt SMG Style Lower Receivers such as the STAG 9 and CMMG MK9