BaxMAX's innovative Thermal (Hot/Cold) Therapy Gel packs are ideal to soothe sore muscles or to use as therapy for injured muscles. This set of 2 gel packs have Velcro sewn to the backside so that they can be attached to the inside of the BaxMAX Back Support. Simply place the Gel Packs in the freezer or microwave before attaching to the BaxMAX.