MasterSeal NP1 Gray Polyurethane Caulk

Master Seal NP 1 is a one-component, high performance, non-priming, gun-grade, elastomeric polyurethane sealant. It requires no mixing and typically requires no priming to bond to many materials, including concrete and masonry. This is our original fireplace mortar formulated especially to patch fireplace fireboxes and to bond firebrick to firebrick. Fireplace mortar is a silicate product that when fire cured, sets rock hard - as strong as firebrick itself and withstands 2000° Fahrenheit. Comes in a convenient cartridge for easy repointing of fireplace brick within the firebox. Colors match most mortars. Suitable for pressure sealing all types of HVAC duct systems including metal, fiberglass