HID iClass technology is the equivalent of Mifare technology in that it operates at a frequency of 13.56MHz. Unlike Prox technology, it allows the information contained on the badge to be modified thanks to an RFID encoder. Clamshell chips are read-only and contain a unique identifier that cannot be modified.
The Clamshell card is not customizable because it is in a thicker format that does not allow it to pass through printers.