When you need maximum coverage and maximum sealing power, take your projects to the max. our new flex seal max is our most economical option, covering up to 20% more than our original size. flex seal max is a rubberized sealant spray coating that sprays out as a liquid. flex seal max seeps into cracks and holes and dries to a watertight, flexible coating. it's the easy way to coat, seal and stop leaks fast.