Robax® HeatWraps with ThermaCare® Technology’s patented Heat Cells use controlled, deep penetrating therapeutic heat to provide back pain relief for up to 16 hours.  By using a combination of ingredients that react when exposed to oxygen, the HeatWraps are active for 8 hours, and you can feel the benefit of heat therapy for another 8 hours. That's 8 hours of heat while you wear it, plus an additional 8 hours of relief after you take it off, for up to 16 hours of back pain relief.  Apply Robax® HeatWraps at the first stages of pain — early application can help keep the pain from interfering with your life.