Mainstay ML-Flex Waterproofing Membrane is a cementitious, acrylic based, flexible waterproofing membrane and coating. It produces excellent adhesion to properly prepared substrates. Mainstay ML-Flex seals rough, deteriorated surfaces and resists negative side and positive side hydrostatic water pressure. This flexible waterproofing membrane is suitable for permanent water immersion service. Mainstay ML-Flex is used primarily to waterproof concrete structures above and below grade and as a lining inside in aquariums, zoos, fountains, water features, planters, and reservoirs.