RFID tags come in a wide variety of shapes and sizes; they may be encased in a variety of materials:
- Animal tracking tags, inserted beneath the skin, can be rice-sized.
- Tags can be screw-shaped to identify trees or wooden items.
- Credit-card shaped for use in access applications.
- The anti-theft hard plastic tags attached to merchandise in stores are also RFID tags.
- Heavy-duty 120 by 100 by 50 millimeter rectangular transponders are used to track shipping containers, or heavy machinery, trucks, and railroad cars.
RFID devices have been used for years to identify dogs, for a means of permanent identification. Dog owners had long used tattoos, permanent ink markings, typically on the ears. However, these can fade with age and it may be difficult to get the animal to sit still while you examine him for markings.
Many musical instruments are stolen every year. For example, custom-built or vintage guitars are worth as much as $50,000 each. Snagg, a California company specializing in RFID microchips for instruments, has embedded tiny chips in 30,000 Fender guitars already. The database of RFID chip IDs is made available to law enforcement officials, dealers, repair shops and luthiers.