Pumie Pool Blok Pool & Spa Cleaning Block, Saver pack of 2 Blocks. Each block measures 6" x 3" x 3". Pumice Stone Swimming Pool Tile and Swimming Pool Concrete Cleaner. Hard Surface Cleaner. Used For Removing Lime, Rust, and Leaf Stains From Swimming Pools. Erases Rust Marks Without Harm. Chemically Neutral. Pool Blok will Not Upset the PH Balance of Pool Water. Works better than your current pool tile and grout cleaner, and it's also easier to use. The block conforms to the shape of your tile and grout, providing better coverage than a regular grout cleaner. Pool Stone Pumice Blocks may be used on Gunite, plaster, tile, grout and concrete of in-ground pools and spas. Pool Stone is an excellent tile and grout cleaner. Not recommended for use on overglazed tile decorations, vinyl, acrylic fiberglass, wood or polished metal surfaces, above ground pools or plastic liners. Pool Blok Pumice stones will restore and revive your pool tiles. Porcelain is harder than pumice and so you can use a pumice stone or stick on any porcelain surface - but not on fiberglass or other scratch able surfaces. Works great on toilets, bathtubs and sinks. These sticks are easily are shaped to fit hard to reach areas. Try the smaller size for small tight places, the medium size for tougher jobs and the large size for cleaning areas like pool and spa tiles from mineral deposits.