ER Systems H.E.R. Flashing Grade Polyurethane Sealant is a single component moisture-cure polyurethane roof coating. H.E.R. is used for waterproofing metal roof seams and fasteners and flashing around penetrations where roof movement causes cracking and moisture penetration. H.E.R. is also used to seal gutters. Stock in 20 oz. sausages, 1 gallon and 5 gallon pails.