Machined aluminum free-float handguard employs a unique barrel nut and rotary-locking system to ensure proper alignment of top rail with receiver rail. Handguard slides over barrel and gas tube at an offset angle, until the notched barrel nut indexes in the internal grooved channel for a secure fit. Two hex head screws lock down the handguard, and a built-in stop prevents over tightening. Vent holes let heat escape the barrel and minimize weight. White alpha-numeric designators on the cross-slots ensure easy repeatability of accessory positions. Streamlined Alpha models have a single, top Picatinny rail, deep horizontal grooves for a secure no-slip grip, and additional ventilat Mfg: Troy Industries SPECS: Machined 6061 T6 aluminum, hardcoat anodized, TeflonA(R) coated, matte black finish. Each model available lengths listed below. Mounting hardware and instructions included. Alpha fits AR-15/M16 rifles and carbines and attaches to the factory barrel nut.