Powerful pain relief + Deep muscle relaxation. Air-activated relief, one-time use. Air-Activated: Just open pouch; starts to warm on its own. 8 Hours of Heat: Long-lasting relief. Ultra-thin, comfortable, discreet, odorless. ThermaCare back/hip is designed to fit the following pant/waist sizes: Women's Pant Size: 4 up to size 20; Men's Pant Size: 28 inches to 47 inches. Made in U.S.A.