The Sons of Liberty Gun Works M4 Complete Upper Receivers stand for high-quality upgrades or replacement parts for your AR-15 arsenal. Originally developed for Sons of Liberty's most popular M4-89, M4-L89, M4-76, and M4-EXO3 models, they are designed to meet all modern standards in the semi-auto rifle industry and elevate the performance of any compatible AR-15 build. Thanks to their rugged construction machined from 7075-T6 aluminum with excellent characteristics, the SOLGW M4 uppers are very resistant to extensive duty use, wear & tear, temperature changes, moisture, and corrosion, which makes them reliable in any condition and situation, from shooting at the range to complex tactical operations. The SOLGW M4 complete uppers feature M-LOK compatible handguards, with a top Picatinny-style rail for mounting various shooting accessories, from optics to lights and Mil-spec grips. The heat dissipation of these handguards is excellent, making them safe to use, and a quality gas system is responsible for recoil reduction for added comfort and balance. The Sons of Liberty M4 Upper is an excellent addition to virtually any AR-15 set-up that can transform even a cheap AR-15 into a professional-grade firearm in minutes.