All San Tan Tactical STT-15 and 6ARC rifles are designed from the ground up with one goal: reliability. Every part of the rifle has been carefully selected to work together as a reliable workhorse. The core of San Tan’s rifles is, of course, the flagship Pillar billet receiver set made of 7075 T6 aerospace-grade aluminum, featuring a full suite of ambidextrous controls including bolt releases and magazine releases.