The ruminal bolus is a ceramic RFID LF (134.2 kHz) tag used for electronic animal identification. There are three models of bowling pins of different sizes and weights that are generally used for cattle, sheep and goats.
Each ruminal bolus has 15 unique international digits and cannot be changed. The ruminal bolus is implanted orally using a special applicator and is positioned in the stomach where it remains for life. The bolus is identified through an RFID LF reader.