MAPEI Keracolor U (Unsanded) Grout in Black is a premium-grade, polymer-modified Portland cement grout. The 25 lb bag is designed for narrow grout joints from 1/16" to 1/8" and is ideal for polished stone, mixed-material mosaics, and glossy glass tile without scratching delicate surfaces. Coverage varies by tile size and joint width, typically ranging from 100 to 500+ sq. ft. It is pre-blended and requires only water for mixing, or MAPEI Grout Maximizer can be used instead to improve stain resistance and flexibility.