Black Rain's Lower Parts Kit includes a buffer retainer and spring, selector, bolt catch spring/retainer/catch/and roll pin, mag catch, two of each takedown pivot pin springs and detents, mag catch spring, mag button, pivot pin, grip screw, star washer, selector detent spring and detent, takedown pin, colored anti-rotation pins and a Magpul MOE pistol grip. This model has black anti-rotation pins and grip, and features Black Rain Ordnance's 3.5-lb. single-stage drop-in trigger.