Pecora XL-Flash is an integral part of the Pecora XL-Perm System, a four step approach for complete air and vapor barrier protection for your building envelope. Pecora XL-Flash is a unique one part, fast curing, non-sag elastomeric STPU (Silyl-Terminated Polyurethane) gun grade, trowelable liquid flashing and joint sealant specially formulated for the Air and Vapor Barrier Industry.