HYVAT is a special 3 layer fabric that insulates, is waterproof and gives protection from cold and moisture infiltration. Also guards against evaporation and promotes ventilation. Made of a proprietary three-layer configuration that incorporates two different microporous layers. The fabric is specially treated for water repellency. These military ECWCS Generation 1 HYVAT Trousers feature a reinforced seat & knee, leg zipper w/velcro cuff, snap-flap access pockets,zip fly, drawstring waist,taped seams. Rothco