Duram S900 is a clear penetrating siloxane sealer that provides invisible, breathable waterproofing for porous surfaces. It soaks deep into concrete, brick, and sandstone to form a powerful sub-surface barrier against water, salt spray, and efflorescence. Unlike surface films, it lets the substrate "breathe," preventing moisture traps and damage. It preserves the natural look while drastically reducing water-related issues like mold, corrosion, and freeze-thaw damage. The ultimate protection without changing your surface's appearance.