Small enough to fit on a key ring. Universal compatibility with HID proximity readers. Offers universal compatibility with all HID proximity 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. 50 Pack Card Data L - Programmed, Low Frequency (125 kHz) HID. N - ProxKey III - Black with grey insert. Includes HID Standard Artwork S - Standard M - Sequential Matching Internal/External (Inkjetted). N - No Option. It comes with a preassigned facility code.