Cold pack based chest and breast coolers: These use Cool 58® Phase Change Cooling Packsto provide direct cooling relief in any climate. Packs fully charge (freeze) at 58ºF (14.4°C) and provide a comfortable, constant cooling temperature of 58ºF. Packs are kept necessarily small and lightweight, therefore the cooling time is less than in other applications. Generally up to 1.5 hrs. depending on a number of variable factors. These packs can be recharged in a container of ice water in just 10 to 15 minutes! Additional time required if activating packs in the refrigerator. We do not recommend a freezer for this product as the pack will be too cold to wear safely and comfortably.