Great size handwarmer, small enough to slip into your gloves or convenient enough to put in your pockets, to keep your hands warm for a short period of time. Heat lasts a shorter time than disposable packets, about 20 to 30 minutes, but these are reusable. -Perfect for walking the dog during the winter season, or warming up hands or feet before bed, baiting fish when ice fishing, when playing in the snow, etc. -Should not be kept in below freezing temperatures as it can"t be activated then. If it crystalizes in these conditions, simply boil to reuse. -The pack starts off liquid. You "click the disc" and it immediately starts to crystalize and warm up to 130 degrees F. -When it is no longer warm, you can put it into boiling water for 5 to 10 minutes, and the crystals will turn back to liquid and be ready to use again by clicking the disc. How it Works -By clicking the floating disc inside the pack it forces molecules to flip to a solid state, and the rest of the liquid rushes to solidify too. The temperature of the solidifying liquid jumps up to 130 degrees F in the process. -The solution inside is sodium acetate, which is a food additive, so is non-toxic and completely safe. It can be reused over and over and over again...a great cost cutter! -Perfect for gifts. -Will come with 4 boxed handwarmers in a high quality glossy gift bag by Totes by Design®, with white tissue paper, "A GIFT FOR YOU" gold medallion on the front, and instructions to reactivate and suggestions for use. -Lifetime Guarantee is offered by the manufacturer. Details are on each box.