They are pre-gels and do not require additional creams or gels. The durable integral structure allows patients easily removing by pulling up from the leaf tail without damaging the structure; up to 30 times reusability by using in the right way. They are companion for most TENS units, or Electrical Muscle Stimulation Machines that use the industry standard 3.5mm Snap on Connector. Medical Grade Reusable Electrodes: bio-compatible, non-irritating, latex-free and superior environmental adaptability of hydro-gel.