R&D Precision AR-15 9mm 5 inch Upper Receiver Socom 1-10 Twist 1/2x36 Comp/Brake Hybrid Black. Unlike the the Gen 1 Upper Kit the Gen 2 comes with a built-in handstop and an updated muzzle device. The upper comes installed with an R&D Precision 6" handguard and a 5" barrel W/ a installed muzzle device that sits about an inch past the handguard. Specifications for R&D Precision AR-15 9mm 5 inch Upper Receiver: Manufacturer: R&D Precision Overall Length: 16 in Barrel Length: 5 in Barrel Profile: SOCOM Barrel Twist Rate: 1-10 Threads per Inch: 1/2x36 Finish: Hard Anodized Aluminum Color: Black Fabric/Material: Aluminum/Steel Handguard Length: 6 in Handguard Style: Hybrid Rail Gun Make: AR Platform Gun Model: AR-15 Weight: 0.6 lb Barrel Material: 4140 Chrome Moly Bolt Carrier Group Included: MIL-SPEC Charging Handle Included: MIL-SPEC Projectile Caliber: .355 Caliber Features of R&D Precision AR-15 9mm 5 inch Upper Receiver Utilizes R&D Precision LLC Patent Pending design Matte black hard-coat anodized per Mil 8625 Type 3 Class 2 Manufactured to MILSPEC (where applicable) on state of the art CNC equipment for consistent quality parts and exacting tolerances Rear vertical Picatinny rail attachment point included. QD Sling Mount Socket built into the rear vertical rail and either sides of the handguard. Compatible with most standard mil-spec AR-15 components and aftermarket parts Package Contents: R&D Precision AR-15 9mm 5 inch Upper Receiver What firearm models does the manufacturer say R&D Precision AR-15 9mm 5 inch Upper Receiver is compatible with? The manufacturer suggests that R&D Precision AR-15 9mm 5 inch Upper Receiver is compatible with AR-15R&D Precision RD8292PW92: AR-15 9mm 5 inch Upper Receiver Socom 1-10 Twist 1/2x36 Comp/Brake Hybrid Black