The M4 Monolithic displays fresh ingenuity with Mil-Spec hammer and trigger pivot pins, a Magpul MBUS iron sight and a folding front sight for enhanced optical solutions, a straight gas tube and a removable lower rail which provides modularity for under mounting accessories. The patented one-piece monolithic upper receiver incorporates a continuous Mil-Spec rail from the rear of the upper receiver to the front sight. This feature affords unmatched repeatability for mounting optical systems, not found with separate handguard rail systems. Designed with accuracy in mind, its true free-floating barrel provides the enhanced accuracy necessary for long-range acquisition capability. Mfg: Colt