20 hr Complement 40hr and 30hr because they heat up quicker and to a higher temperature. Good to use together!
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 up to 40+ hours...Excellent Heat Pack for shipping live corals, insects, reptiles, fish, flowers, etc.
Designed to heat up an insulated box less than 12" cubic inches in size, NOT a room.
