Metacaulk® 350i is a one-component, general purpose fire-rated sealant and smoke seal for construction joints and through-penetrations. Metacaulk® 350i is an intumescent, water-based, non-sag caulking grade sealant that is easy to apply and great for retrofits. It cures to an elastromeric seal that is suitable where dynamic movement is expected. Sound Transmission Class (STC) rating 53, Tested in a UL 411 wall assembly/section to ASTM E90.