OSI H2U Window, Door, Siding and Trim Sealant is a high-performance sealant designed for the siding and window industries. This superior acrylic urethane formula has better adhesion, flexibility and durability than most sealants, and cleans up easily with soap and water. This water based, low gassing formula is ideal for use indoors and provides the durability, flexibility and adhesive strength needed for outdoor use. OSI H2U dries to a glossy sheen and when fully cured it is paintable and will resist surface mold and mildew.