Home / Rails / AR-15 Rail Systems / Rail System Wrench & Extra Parts Rail System Wrench & Extra Parts Barrel Nut for (SOT) (556 SD) Rails $49.99 In stockAdd to cart Barrel Nut for (SOT) 308 Rails $44.95 In stockAdd to cart Barrel Nut for (SOT) 556 slim rails $29.95 In stockAdd to cart Barrel Nut Wrench 556 Series Rails $15.25 In stockAdd to cart Rail Extra Parts Pack $5.95 In stockAdd to cart