Grub's Nora Thermo Wellington Boots - Olive The Nora-Therm Superior Polyurethane boots are a comfortable and lightweight solution to extreme cold temperatures. Noratherm is made from Polyurethane, which contain millions of tiny air bubbles making the boots lightweight and giving excellent thermal insulation. In addition, hydrolysis protection and anti-UV additives make Noratherm hardwearing and durable, lasting up to 3 to 4 times longer than traditional PVC and rubber boots.