Because of its thicker consistency and the fact that it is water based, CADS is one of the best mastics on the market. These same factors make it easy to apply to both damaged fiberglass insulation and leaking sheet metal ductwork with either a hand, brush, or trowel. This mastic is fiber reinforced for a stronger seal. Excellent mildew resistance. Can be used on indoor or outdoor applications. Priced by the gallon. Unopened shelf life of 18 months.