4" x 6" (100 per Box) These gel packs are non-toxic and can hold a hot/cold temperature for up to 30 minutes. They are soft, durable and will remain flexible even at 0 degrees. Hospital proven, latex-free.Therma-Kool reusable gel packs are designed to provide comfortable pain relief when cold or hot therapy is required. Therma-Kool remains flexible when frozen for up to 30 minutes and is safe for microwavable use. Use cold for the treatment of sprains, strains, headaches, contusions, bruises and minor bleeding/burns. Use hot therapy for temporary relief of muscle stiffness, aches and pains. Hospital proven, latex free, non-toxic and easy to clean for reuse. Preferred by School Nurse!