The STT PILLAR upper receiver is the lightest billet upper available today! STT wanted to create something better, something different. Being better was not enough -- STT needed to design an upper that overcame the shortcomings seen in the current offerings . It needed to be lighter, stronger, and different, and all while looking good doing it. SST wasn't going to settle for just hacking another receiver out of a block and calling it good. The first thing people will notice is the truss pockets. With the shooting styles of today's shooters everyone wants to run 15" & 16" long rails and grip the rail as far out as possible to gain the most control of the rifle. That's like attaching a 16" lever to the rifle. The truss design acts similar to a bridge that carries and distributes the stress across the entire platform verses putting all of the stress on the material right behind the threads of the receiver. The extra strength gained from this design is not only to help the receiver. It also in turn helps improve your accuracy. When most people think of a billet receiver they think of a blocky, heavy, thick design that is CNC machined. STT wanted to break that mold too.