Mapei Ultralite S2 Highly Deformable Lightweight Mortar with Polymer, WhiteSetting tile? Ultralite S2 Highly Deformable Lightweight Mortar with Polymer, White is the thinset that goes between your tile and the substrate. Lightweight formula covers more square feet per bag and is easier on your back during install. Same coverage you'd expect from a standard thinset, less weight per pound to carry up stairs. White color so it doesn't telegraph through translucent tile or light grout joints. LEED