These handguards are designed to replace your standard plastic handguards with our 4 rail picatinny design. Simply remove your existing handguard panels and insert these in their place. No gunsmithing required! They are made from lightweight aluminum and hardcoat anodized. The bottom rail removes easily to accomodate accessories such as grenade launchers, flare launchers and shotguns. Note: This rail will NOT fit Colt carbines