PermaFlex 275 is a non-modified, medium bed mortar designed for setting large format tile, where the embedded thickness is between 3/16 in. and 3/4 in. It is ideal for use over uncoupling membranes, especially where a non-modified mortar is specified. It provides good workability for interior and exterior installations over concrete and helps overcome irregularities in tile thickness. ProSpec/Amerimix.