Siena Pro Set Flex M300 is a flexible polymer-modified mortar manufactured with a mixture of Portland cement, graded aggregates and other proprietary additives to produce a high quality mortar that does not require soaking of tiles to give higher bond strength, higher flexibility, greater open time and coverage than standard mortars. Siena Pro Set Flex M300 will span minor cracks of up to 1/16” (1.6 mm) in substrates with limited vibration and deflection. It is available in either white or gray color and complies with the requirements of ANSI A118.4 and A118.11.