Mapei Mapeker is a rapid-setting, cement-based tile adhesive suitable for both interior and exterior installations of ceramic and porcelain tiles, as well as non-moisture sensitive natural stone. For light-colored natural stone, use the Mapeker Rapid-Set Flex in white. The grey or white versions are also ideal for spot bonding various insulating materials, including expanded polystyrene, polyurethane, gypsum board, glass and rock wool, wood-cement panels, formed concrete blocks, and sound-deadening panels.