Ultimate Arms Gear PROB Black 5.56/.223 2 Piece Modular Mount + LTFCR Black 4/5/7 Slots Combo Pack 2 Piece Design with Upper and Lower Shields for Maximum Cooling. Weighs 4.5 ounces. USA MADE Designed and Engineered to Accommodate Gas Piston or Direct Gas Impingement System. Hand Stop and Textured Surface. Slots Light Weight Polymer with High Strength Fibers. Bolts and Lock Washers Included.