NSi firestop intumescent caulk is water based, single component elastomeric sealant intended for use as a firestop system component. It forms an economical yet durable, flexible and watertight bond with most construction materials. It is applied independently for caulk and walk systems or over mineral wool or backer rod to seal the Openings where building services such as pipes and cables penetrate fire rated assemblies. Will not crack or crumble as the physical properties remain stable over time. It tools easily and cleans up with water. Astm-e 814 and UL 1479. 10.3 fluid ounce cartridge.