• Ideal for shipping perishable or heat-sensitive materials – concentrated cold lasts longer than ice

The refrigerant is designed to protect your product from freezing or over-heating even in extreme conditions. Gel filling is nontoxic, nonhazardous and biodegradable; won't contaminate samples. Reusable packs freeze solid in 6 to 10 hours and remain at constant temperature for up to 72 hours. Place packs in the freezer for 24 hours before use. Gel changes phase (freeze to thaw) at 0° C (32°F)