Iron-Grip 601 is a versatile, all purpose, fber-free, duct sealant for use on all types of metal duct, fberglass duct board, duct fabric and fex duct. Distinguished by its ability to accommodate minor vibration and movement, Iron-Grip stays fexible and does not crack. Iron-Grip's excellent coverage rates and easy brush-on application provide low installed cost while providing Hardcast's proven reliability.