Design FX Grout is ready-to-use and accentuates the natural beauty of glass, mosaic and metal tiles in addition to ceramic, porcelain and most natural stone tile. For use in tile joints from 1⁄16" to 1⁄2" (1.6-12 mm) on floors and 1⁄16" to 1⁄4" (1.6-6 mm) on walls. Design FX grout is stain proof*, approved for interior and exterior use and is rated up to moderate commercial use. * Design FX grout is stain proof to most common household, residential stains when cleaned immediately. The prolonged exposure of any stain will increase the likelihood of permanent staining or discoloration of grout surface.