Clever Top/Bottom Two-piece Design with Integral Spinal Cords/Alignment Housing for Perfect fit with Barrel Nut and Round Front Cap. Fits Car. Length Model 4/15 and Provides Four Picatinny Rails Each with 14 Slots. Great Zero-retention Capability for All Accessories Installed on the Rails. Easy Installation with No Modification to the Barrel.<br />NOTE: This quad rail system is designed to fit with standard AR15 gas tube. The compatibility with any special piston system is not guaranteed. <br /><br />Note: <br />Please make sure the mount fit before your purchase