Keep your water cool in the heat and help prevent freezing in the winter. Water Bladder Reservoir Insulation and Protection. Easy Installation. ****(Water Bladder and Drink Tube Cover NOT included)**** See Size Chart Picture and READ description below to order correct size. Veteran Owned Business and Made in the USA Bladder Insulators will help insulate your hydration backpack water bladder – reservoir. These bladder insulators are compatible with Hydrapak water bladder reservoirs to provide insulation against harsh weather elements.