Sharps Bros. Full Top Rail M-LOK Handguard 15in Black. Handguard is made of 6061-T6 aluminum and anodized black per mil-spec MIL-A-8625F TYPE III CLASS 2. The barrel nut is 4140 PH steel. Full top rail + MLOK slots on 7 other sides. Includes anti-rotation tabs. Installation: Use standard castle nut wrench & torque wrench. Torque barrel nut to 40-55 lbs. This is typically done 2-3 times e.g. torque to 40-55lbs then loosen then torque again to 40-55lbs then loosen then torque to 40-55lbs one final time. Hand tighten barrel nut/handguard screws using 1/8" hex drive. Then torque screws to 30-35 inch/lbs Specifications for Sharps Bros. Full Top Rail M-LOK Handguard: Manufacturer: Sharps Bros. Color: Black Finish: Anodized Fabric/Material: 6061-T6 Aluminum Gun Make: AR Platform Gun Model: AR-15 Gun Type: Rifle Handguard Type: Free-Float Handguard Style: Quad Rail Gun Rail: M-LOK Full Top Rail Gas System Length: Rifle Length Height: 2 in Mount Type: M-LOK Package Contents: Sharps Bros. Full Top Rail M-LOK Handguard Barrel Nut Hardware Anti-Rotation Tabs Sharps Bros. SBHG05: Full Top Rail M-LOK Handguard 15in Black