DoorBird 125 KHz Transponder Key Fob, 64bit, Write-Protected, Material ABS, for D21x and Later, 10 PiecesTo be used with DoorBird D21x models and later Comes with 10 RFID Key Fobs 64 bit encryption and write protected Great for access control. Set times and dates to allow entrance DoorBird Units are designed and made in Germany Comes with 10 pieces 64bit rated and write protected. Works with D21x and later models