I have one somehow from physical therapist stating it was effective to my Dr and the one I have I mightve been sent home with to use but became mine (legally) after a certain amount of time? I dont remember. I do remember the co. sending a envelope to mail it back after it was charged to ins. and I called to check and they said Oh no that was a mistake. It was paid for by ins. so its yours to keep. New electrodes come monthly. I stopped new ones from coming because I have enough and know our healthcare needs all the help it can get.