These are cold packs that are filled with a non toxic gel and frozen before shipped. One pack can keep yeast cool for up to 3 days in transit. In the summer, we suggest adding one extra ice pack for each extra day of travel, and at least one of these for every 2- 6 yeasts, especially in the hotter months. These packs are FROZEN when shipped, thus we advise you purchase no more than 1 Gel pack for every yeast ordered. The yeast may freeze if packed with too many gel packs.
These ice packs can be reused dozens of times; simply re-freeze and they are ready for an ice chest or other application.