Compact gas block clamps securely to barrel with a unique three-point attachment system to provide a solid accessory mounting platform and ensure proper gas system alignment for reliable cycling. Precision machined from high-grade 6061 T6 aluminum for an ideal combination of strength and low weight, with an integral MIL-STD 1913 Picatinny rail on the topside. Anchors to the barrel with a pair of hex-head setscrews on the underside, plus a third screw on top to ensure a superior gas seal and resist unwanted movement that can impair gas system function. Streamlined design has clean, good-looking, angular lines with all exposed edges radiused to eliminate sharpness. Mil-spec hardcoat anodize Mfg: Double Star SPECS: 6061 T6 aluminum, hardcoat anodized, matte black. All models 1.875" (cm) long. Rail heights are measured from top of barrel to top of rail. .625" - 1" (2.5cm) wide, 1.5" (3.8cm) overall height, .600" (1.5cm) rail height. 3 oz. (84g) weight. .750" - 1&rdq