RFID TAG 125kHz EM designed as Cylinder in Black Plastic

The most frequently used 125 kHz transponders – also called TAGs – are of the "read only" type - i.e. they are provided with a unique ID code of up to 40 bits during fabrication, which cannot be changed.

TAGs are available in a range of different designs. For example round pieces in various sizes and formats, as key tags and as credit cards. Only the most popular types are shown here.