Simple to use Heat Pack! - Just open, unwrap, and let sit for 10+ minutes to start the heat process. Put Shipping Item in Shipping Bags and Seal to Lock in the Heat. For Extra Protection, Use Bags Double Bagged for Even Better Insulation From the Cold. Designed for reliable and steady heat release for 30+ hours...Excellent Heat Pack for shipping live corals, insects, reptiles, fish, flowers, etc. Provides an average warmer surface temperature of 100 degrees Fahrenheit