Featuring a luggage-grade, 1000-denier nylon outer shell, and heavy-duty YKK #10 zippers, the Polar Bear 6 Pack Nylon Soft Cooler is built to last. Don't let the size fool you! Polar Bear constructs their smallest cooler with the same high-density foam insulation that they put in their larger Nylon Soft Coolers. When packed correctly, you can expect 24 hours of frozen ice in heat up to 100 degrees Fahrenheit.