USB CLASSIC LIGHT is a highly breathable, 3 layer, impermeable membrane; the top and bottom layers are made of non-woven polypropylene fabric which protect the middle UV 10 polypropylene film. The three layers are joined and heat sealed together. Its areal mass of 155 g/m2 makes USB CLASSIC LIGHT the lightest breathable membrane for roofing use (in accordance with UNI regulations only for slopes of more than 30%), but at the same time it is the heaviest and strongest of the breathable wall membranes, as a thermal cladding coating for ventilated walls.