Stopper with natural rubber seal and reinforced metal thread for a perfect seal. The surface is designed to allow a gradual approach to the heat. Indicated to reduce muscle spasms and for disorders that require prolonged application of heat. Benefits: Made with natural rubber and PVC to ensure longer lasting heat Provided with cover to prevent direct contact with body How to Use: Remove the cork of the hot water bag and fill with adequate quantity of hot water If too hot please be careful, directly apply to the affected area.