Hothands® Adhesive Insole Foot Warmers are perfect for anyone wanting safe, convenient, concentrated warmth in cold weather conditions. The insole warmers have adhesive on one side to keep them securely in place in your shoe. Insole warmers are air activated and ready to provide up to 9 hours of long lasting heat! Keep your feet warm on your next hike or in your trunk for your next road trip!. Item Specifics: Size: 9.75 in x 4.5 in Maximum Heat: 109 Degrees Average Temperature: 99 Degrees One size fits all.