The Troy Enhanced Drop-In Rail is a non free-floating direct replacement for M4/AR15 plastic handguards. The Troy patented clamping design ensures a solid clamping design ensures a solid mounting platform and provides a true optical mounting platform that increases the modularity and accuracy of the M4.FeaturesMachined from hardened aircraft aluminum with stainless steel componentsInstalls in minutes with 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 Notes:9" version is designed for a triangle end cap7" version is design for a round end cap