This genesis of modular free-float rails has arrived, building off the TRX Extreme design. The Alpha Rail utilizes a low-profile locking mechanism which offers unparalleled strength and stability. This model comes With a built-in M4-style Troy spring-loaded front BattleSight. The Alpha Rail disperses heat and runs cooler than other close-to-the-barrel rail systems. With unlimited mounting options and greater heat dispersion, the Alpha Rail comes with three detachable rails and all mounting hardware. It is machined from 6061-T6 hardened aircraft aluminum and finished in Mil-Spec Type III Hard Coat Anodizing. Works with standard AR15/M16 barrel nut (no barrel nut included). Note: 13" Alpha Rail with built-in sight is not compatible with rifle- or intermediate-length gas systems. Alpha rails do not work with the TRX barrel nut or wrench.