Priority One Cast Stone Mix brings new possibilities to architectural cast stone. Our unique formula uses the highest-quality limestone—rather than gravel—to create a more natural look with richer, more accurate colors. New proprietary technology gives our optimized cast stone mix incredible strengths — over 7,000psi compressive and 1,600psi flexural. This strength allows our product to be cast a 1/2″ thick over a foam core; resulting in less material, lighter weight, and easier installation. A strict quality-control program ensures our bags are consistent in color, weight, and material.