PS 42L is a polymer modified dry set mortar composed of lightweight aggregates, sand, cement, dry resins and other proprietary chemicals used to adhere virtually all types of tile, especially large tile units, marble, and granite to acceptable surfaces. Due to its light-weight and flexible properties, PS 42L installations provide higher resistance to cracking than normal mortars. PS 42L is especially formulated to hold large units in place on vertical surfaces. PS 42L also reduces unevenness caused by setting of the tile when used on horizontal surfaces.