SLR Rifleworks HELIX MLOK Handguard - F ModelExcellent feel for todays modern shooters No timing of barrel nut required, no shims needed Works with any receiver forged or billet 1. 35" ID Mil Spec Hardcoat Anodize 7075 Barrel nut w Hardcoat Anodize Melonite Finish Hardware Free Floating Design Proven Slip fit locking mount design, much more secure than a clamp type mount. Billet Anti Rotation Insert (black insert included) Proven Anti Slip Design keys into barrel nut Barrel nut uses standard