Hevea of Holland is the first manufacturer of Wellington boots made from foamed polyurethane (PU).  These are half the weight of a comparable PVC boot. Take few thousand steps and that's a ton you're not lifting every day.  The PU is all things good in a boot.  They'll wear twice as long as PVC or rubber , are 3 times warmer because the PU traps millions of microscopic air bubbles just like a divers wet suit.  The real beauty though is the comfort and flexibility of the Hevea's.  They have become known as the fisherman's slipper.  How many hours a day do you spend in your boots?