When most people think of a billet receiver they think of a blocky, heavy, thick design that is CNC machined. San Tan Tactical STT PILLAR Billet AR-15 Upper Receiver broke that pattern. Their receivers are Cut from a single billet 7075 -T651 aerospace grade aluminum. Thru the use of 3D CAD modeling software, they were able to save weight in places that extra material didn't have a purpose, such as the forward assist block and the shell deflector. These spots are often very bulky on other billet sets due to the difficulty of removing material on all of those angles. After all of was said and done the new STT upper receiver came in at only 8.2 ounces. FeaturesM4 Feed RampsShell DeflectorMilspec Ejection Port Cover