Non-Hazardous cooler gel pack out performs ice and other gel packs. Originally designed to keep blood shipments cold, these packs have as much energy as a freezer. Packs are designed to phase-change at 18° (go from solid to liquid). This releases the largest amount of energy at freezer temperatures to get your food and beverages cold quickly. Put them in the freezer at 0° (typical freezer temp.) for 24 hours and you will have portable cooling power that actually accelerates cooling (cools things down rather than try to keep them at the temperature they started at. Easy instructions included and video at CoolerShock web site. Pack turns to gel in 15 minutes. It last all day (24 hours) under constant use and opening and closing of your cooler (in size matched coolers listed at website) These reusable bags are the perfect alternative to traditional ice. The simple math is that each time you fill your cooler with 10 lbs. to 20 lbs. of ice you spend $5-$15 dollars and its gone at the end of the day. Dry cooler packs are a great value and our biggest seller. Cooler Shock is a gel when warm and a solid block when frozen.