Sponge Rubber can be formulated into several different elastomeric materials in a variety of densities. It is a highly flexible material that can adapt to seal almost any surface application when used with pressure sensitive adhesives or with Heat Activated Tape Systems (HATS). Sponge Rubber is composed of individual cells that are a lot like balloons; they hold in gas and do not allow moisture to penetrate their walls so long as the cell walls do not burst.