Thermacare Back Heatwraps are designed to provide you with instant pain relief for tight and tired muscles and can help restore them to their normal state. These discreet pads are worn under clothing and will provide therapeutic heat that lasts for up to 16 hours. That's up to 8 hours while you wear them and 8 hours of relief after you take them off. They contain heat generating ingredients including; iron, charcoal, salt and water and can penetrate deep to relax tight muscles so circulation flows in. The constant heat provided by Therma Care increases blood flow to tissues, giving pain relief which last even after the wrap has been removed. As muscles relax, more oxygen is provided to the damaged tissues, helping to restore aching muscles. Key Features of Thermacare Back Heatwraps Best ever fit for more targeted relief Patented heat cells for deep penetrating heat Up to 16 hours pain relief when worn for 8 hours One size fits all Drug free relief from muscle and joint pain Contains 4