NPT SMSHEAQU 3" x 24" Step Marker Shells Aqua - These sometimes elegant, sometimes playful tile murals are frost proof and ideally suited for application in swimming pools, on interior and exterior walls, as tile backsplashes, countertops and even floors. All tile products are frost proof, virtually maintenance free and guaranteed for the life of the installation. The complete range of tiles meets or exceeds all industry quality standards including freeze thaw resistance and chemical resistance.