The utg pro m4/ar-15 carbine length drop-in quad rail with extension top rail extends to upper receiver to form continuous mounting platform.The top/bottom two-piece design has integral spinal cords/alignment housing for a perfect fit with the barrel nut and round front cap.It is precision cnc-machined from from aircraft aluminum with anodizing/engraving.The four picatinny rails each have 14 slots with great zero-retention capability for all installed accessories.Easy installation with no modification to the barrel.Black rubber rail guards included.Note-this quad rail system is designed to fit with standard ar-15 gas tube.The compatibility with any special piston system is not guaranteed.Made in the usa.Rails: PicatinnyType: Railed HandguardFirearm Type: AR15 CarbineFirearm Model: AR-15Material: AluminumFinish: AnodizedFeatures: 14 Sections Per RailPositions: 4