Water based fiber reinforced duct sealant/mastic formulated for indoor/outdoor use. Meets U.L. Class 1 rating and local codes while featuring long term flexibility and strength. Use on metal heating, ventilating and A/C duct systems, as well as fiberglass duct board systems and flex duct systems. Recommended for use to 10 in. Of water column pressure without the need for fiberglass mesh reinforcement. Diversitech Pro-Air Duct Sealant, Tube, 10.5 oz, Water Soluble Base, White, < 37 % VOC