FORMAT HS is a prefabricated waterproof styrene membrane made from a special distilled bitumen compound modified with propylene and styrene blends, and a heavyweight polyester staple-fibre nonwoven carrier, reinforced and stabilized with glass strands parallel to the machine direction. The compound provides very good low temperature flexibility properties. The FORMAT HS membrane is produced to the quality standards set by NAT^® technology, the innovative manufacturing system for the control of polymer matrix ageing in bituminous membranes.