Rosco handguards are machined from 600 series extruded aluminum and are designed to be strong enough for any environment. The narrow cross-section of the hand guard provides for an excellent ergonomic grip while the M-LOK mounting system provides a smooth, hand-friendly surface in place of Picatinny rails. 6000 series extruded aluminum Milspec Type 3 Class 2 hard black anodized rail 7075 aluminum Type 3 Class 2 hard anodized barrel nut Anti-rotation tabs align rail to upper receiver No barrel nut shims required for installation Does not contact or apply side loads to gas tube Inner Diameter of handguard - 1.315" MLOK Slots on all flat sides (7) Includes barrel nut wrench Barrel nut diameter- 1.378" Compatible with most known low profile gas blocks 11.7 ounces - total weight including mounting hardware Made & Assembled in USA