No matter how many options emerge in the massive AR-15 market, there's always going to be a demand for that classic, M4-style configuration that's been proven on battlefields across the world. Now, you can have an AR-15 that's built to the same standards and with the same features as the M4 Carbine that's served with our military for decades. This is the Stag Arms Stag-15 M4 Upper Receiver. True to form, the Stag Arms Stag-15 M4 Upper Receiver is everything you're looking for in a GI-spec system, complete with the 5.56-NATO-Chambered barrel measuring 16-inch long and complete with a 1:7-inch twist rate. The barrel and chamber are chrome-lined for corrosion resistance, and the muzzle end of the upper is crowned with an A2 birdcage flash hider. Surrounding the barrel assembly is a thermoplastic handguard that completes the look of this classic platform. All you need to do to complete this Stag Arms Stag-15 M4 Upper Receiver is add a bolt-carrier group and charging handle that adheres to mil-spec designs, which certainly won't be hard, and you'll have a close match to the service rifle we know and love.