The Heat Factory Back Wrap is the perfect solution for a sore back. The elastic material is made of veltrex so it can stretch to almost any size. The key feature is the two large warmer pockets. These pockets are designed for the Heat factory Large Warmers which supply you with 24 hours of continuous warmth. This is a high quality backwrap that can be hand washed and can last for years. One size fits most,  Warmers are sold separately