Small enough to fit on a key ring. Universal compatibility with HID proximity card readers. Provides an external number for easy identification and control Can be placed on a key ring for convenient entry. Supports formats up to 85 bits, with over 137 billion codes. Using HID's ProxProgrammer®, card vendors can ship proximity keyfobs, custom programmed to their customers' requirements, from their own inventory. Enables smaller order quantities and overnight delivery. (Check with vendor for availability.) Lifetime warranty.