Ibutton Probe DS1990A and DS1991L Serial Number iButton is a rugged data carrier that acts as an electronic registration number for automatic identification. GYRFID provides Ibuttons, keyfobs, wristband for different use style. Low-cost electronic key for access control. IBT – ibutton ring only, metal component dia17mm × 6mm TM - TM Keyfob with handle TM-R – magnet TM key, magnet ibutton with holder WRA04- wristband with ibutton