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. 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 sets comes with three detachable rails and all mounting hardware. Works with standard AR15/M16 barrel nut (no barrel nut included). Includes two 2" and one 4.2" detachable rails and all mounting hardware. *Note: Alpha rails do not work with the TRX barrel nut or wrench.