The endura windchill biblongs come with teflon ht treated thermolite which provides extra insulation and comfort all year round it also has a windproofbreathable membrane on the front of the leg ankle and crotch panels to keep the wind away from you as well as supportive mesh upper with high stretch lycra straps for comfort endura windchill biblong features knit fabric with windproof breathable membrane on front leg ankle and crotch panels teflon ht treated thermolite p