For physical cooling and coid compress physiotherapy. The degree above 38℃,the color changes from purple to pink. The degree below 38℃, the color changes from pink to purple. Only for treatment of closed soft tissue. Cooling effect instantly lasts up to 8 hours. Easy to apply and remove and will not leave any sticky residue. Gentle to the skin (Weak Acid gel sheet/Hydrophilic Polymer used).