Omron Gel Refills include 3 pairs (6 pcs) that can be used up to 30 times on the Omron Heat Pain Pro TENS Unit permanent pads before replacing. The conductive gels heat up to 110F for soothing on the spot warmth and pain relief. The Omron Heat Pain Pro TENS Unit is the only device on the market that combines soothing heat for achy muscles with TENS (transcutaneous electrical nerve stimulation) technology to relieve acute muscle and joint pain. Heat Pain Pro offers users customizable pain relief through alternating periods of TENS and Heat, or TENS alone and 6 pre-set body pain and 3 massage modes with 20 intensity levels that can be used on multiple pains throughout the body. Omron Heat Pain Pro TENS Unit provides 100% drug-free pain relief so you can treat the area of pain and avoid the side effects associated with prescription medications - helping you get back to a full and active life.