Heavy - duty vinyl separates these coolers from the rest of the pack. FrostPaks??? are engineered for higher thermal efficiency and a longer lifespan than regular soft-sided coolers.These expedition-proven coolers feature a waterproof liner that prevents melted ice from penetrating insulation and are waterproof up to the zipper.The 12 qt. and 19 qt. coolers are the perfect size for day excursions and hikes. The 40 qt. is shorter in height and longer in length for easy lashing into place, making it a great cooler for rafts and canoes.