6 x 4 x 12 Atlas™ - H.C. Muddox structural brick offers the natural aesthetics and excellent load carrying capacities of brick walls for earthquake and wind loads and contributes towards achieving energy efficient buildings through thermal mass and resistance to water and air intrusion. Structural brick walls offer the highest fire ratings, sound transmission (STC) ratings and low maintenance inherent to brick walls. H.C. Muddox Structural Brick meets all requirements of ASTM C 652.