The 2A Armament™ BL RAIL Gen 2 M-LOK series has styling changes in the picatinny pocketing to match with the Balios Lite Gen 2 or Aethon receiver sets. By utilizing an Aluminum barrel nut, and an innovative 45 degree mounting system, the BL RAIL achieves a solid lockup with the upper receiver. The 2A Armament BL RAIL will ship with a 7075-T6 Aluminum barrel nut. The BL RAIL Gen 2 is a great fit with the new styling on any quality forged or billet upper receiver offered from other manufacturers.