Reach deep tissue for maximized healing and therapeutic effects with this Chattanooga Hydrocollator HotPac set from MassageTools. This heated collar is one of the first topical thermal agents in rehabilitation medicine. It combines moisture and heat to reach tissue as deep as ¾ of an inch. This deep tissue is then heated by the thermal collar to provide soothing pain relief and relaxation. When used as directed, the HotPac can raise temperatures from ¼ of an inch deep to ¾ of an inch deep in approximately 20 to 30 minutes.