Prism® Ultimate Performance Grout sets a new standard in cement-based grout technology. Prism's Calcium Aluminate cement-based formula offers consistent colour with no shading regardless of tile type, temperature or humidity. Formula will not effloresce. The rapid setting formula results in high early strength and dense joints for the highest stain resistance in grout joints up to 1/2". A blend of lightweight recycled glass and fine aggregate sand allows for a smooth consistency that is easy to spread and clean. Oyster Grey. 6.8 lb (3.1 kg).