These unique forearms feature diamond shaped heat vents, an extended top rail for gap-free installation, "T" marked rails to mark accessory locations, they accept our end caps, and utilize our anti-rotation screws for secure installation. The forearms and barrel nuts are made of 6061-T6 aluminum and hardcoated to military specifications. The jam nut and anti-rotation screws are steel and plated a matte black finish to match. Palmetto State Armory, your source for AR15 Accessories!