Metacaulk® 350i is a one component, general purpose fire rated sealant and smoke seal for construction joints and through-penetrations. Intumescent, water-based, non-sag caulking grade sealant that is easy to apply as well as to retrofit. It cures to an elastomeric seal that is suitable where dynamic movement is expected. STC rating 53*. Complies to Required Environmental Exposure Testing of Accelerated Aging and High Humidity as per UL 1479 Fire Test of Through-Penetration Firestops. *Tested in a UL 411 wall assembly/section to ASTM E90.