Troy's Enhanced Drop-In Rail is a non-free-floating direct replacement for all M4/M16 plastic hand guards utilizing the carbine, mid-length, and rifle-length gas systems. Easy to install; no gunsmithing required. Includes MIL-STD Picatinny Rails at 12, 3, 6, and 9 o'clock and four built-in sockets for Q.D. Swivels. Machined from hardened aircraft aluminum with stainless steel components and finished in MIL-SPEC hardcoat anodizing. Mfg: Troy Industries