Tuff-R™ Polyisocyanurate Insulation consists of high-performance, high R-value, closed-cell polyisocyanurate foam core boards sandwiched between a choice of durable exterior foil facers. On Tuff-R™ Insulation, one facer is a continuous sheet of aluminum foil; the other is a Tri-Plex facer consisting of a three-ply laminate of durable kraft with aluminum foil on both sides. Tuff-R™ helps reduce air infiltration through the wall by covering cracks between the framing members and sealing tightly against the studs.