These are our standard premium SELF-ADHESIVE and REUSABLE Replacement electrodes for TENS/EMS units. They are cloth backed and have the common "Snap" electrode connector. These self-adhesive pads do not need extra conductive gel. You can increase the lifespan of your electrodes by keeping them in the air tight package when not in use, cleaning your skin prior to putting the pads on your skin and rubbing a small drop of water on the electrode pad after each use. Opened or used electrodes can not be returned for a refund.