These rewritable key cards can be programmed by Keysy RFID Duplicator to be one-to-one copies of the original keycard/keyfob. They are thin, size of a standard credit card, passive (no battery) and completely waterproof. Any keycard/keyfob that can be read by Keysy can be written out to to one of these rewritable key cards. Five rewritable key cards included. Keysy rewritable Key Fobs available here. Keysy rewritable Sticker tags available here.