Styrofoam™ Brand Sill Seal Foam Gasket is a flexible polyethylene foam gasketing strip that can help reduce air infiltration between a concrete foundation and sill plate, around windows and doors – and even between floors. The closed-cell polyethylene foam compresses to seal gaps in irregular surfaces, helping reduce air infiltration for a tighter building envelope and enhanced energy savings. It provides excellent and enduring resistance to water and water vapor.