Maximize the accuracy of your AR-15. Seekins Precisions iRMT-R Upper Receiver uses Integrated Rail Mounting Technology, which integrates the rail mounting points into the upper. This ensures superior stiffness while allowing the rails to be completely modular. Plus, this design is considerably thicker in the most critical areas all to increase accuracy. Externally threaded steel barrel nut with 1-1/8 wrench flats for easy installation. Compatible with Seekins Precision BAR rail and MCSR rails. Wt: 14.25 oz. (as shipped). Type: AR-15 Uppers.