UTG Pro M416MA Model 4/15 Mid Length Quad Rails. Detail Information: Proudly Designed and Made in USA. Clever Top/Bottom Two-piece Design with Integral Spinal Cords/Alignment Housing for Great Fit. Designed with Innovative Alignment Tabs at the Front for Perfect Fit with the Standard Triangular Front Cap. Fits Middle Length Model 4/15. Includes Four Picatinny Rails Each with 18 Continuous Slots. Great Zero-retention Capability for All Accessories Installed on the Rails. Easy Installation with No Modification to the Barrel. Black Rubber Rail Guards Included.NOTE: This quad rail system is designed to fit with standard tactical .223 gas tube. The compatibility with any special piston system is not guaranteed.