MSI Haiku Sapphire Glass Subway Tile 2x6Marble threshold in natural colorway MSI Haiku Sapphire Glass Subway Tile 2x6 sized for 2x4 format with polished single beveled or double beveled edge, protects cut edges at flooring transitions. Quarried natural marble holds its tonal range across pieces, so a multi threshold install reads as one continuous design move rather than several joined pieces. The polished face stays bright across years of foot traffic with standard marble sealing protocol;