Food Safe - 18 Degrees F. Originally designed to keep blood shipments cold, Cooler Shock has as much energy as a freezer. Designed to phase change (go from solid to liquid). At 18 ? or - 8 ? - This releases the largest amount of energy at freezer temperatures to get your food & beverages cold quickly. Cooler Shock makes things colder over time. CoolerShock formula is shipped dry. You add the water and screw the cap on or zip it and seal it. Pack turns to gel in 15 minutes. Lasts 24-48 hours under constant opening and closing of your cooler. Great for fishing, boating, parties and tailgating. Caution: items placed in direct contact may freeze. Good for 100’s of freeze cycles. Pack durability now includes a later of nylon Increasing durability 50% over any competing product. Our packs have the highest heat transfer rate due to our bag design. If you handle them with a bit of care and avoid tossing while frozen or long-term submersion, they will last for years.