The CR-1632 battery is to be used in the 2nd generation TST Flow Thru Sensor, 1st generation Cap and Flow Thru Sensor. Be sure to look at the pictures in this listing to make sure you are choosing the correct battery for your sensor type. If you need help determining which battery you need then you can call us at 866-324-7915. We recommend changing batteries and O-rings in your TST sensors yearly.