Use these Phase 22 Packs to help maintain shipments between 68F-75F degrees. Changing phase from a solid to a liquid or vise versa requires energy. This buffers the temperature of the surroundings at the phase change temperature. Water-based ice packs change phase at 0C (32F), and are thus great for maintaining shipments near 0C (32F). Not so great for dart frogs however. Phase 22 Packs contain a material that changes phase at 22C (72F), and are thus very efficient at maintaining the perfect shipping temperature for dart frogs and many other amphibians. Shipping during hot weather? Cool pack in refrigerator until all solid before shipping. Shipping during cold weather? Warm pack in hot water until all liquid before shipping. Shipping from a cold to hot location or vise versa? Add a pack in the liquid phase and another in the solid phase.