O2S-FR-T3 has a full porous cap giving a fast (<4s) response time. They require a heater voltage of 4.35V.

O2S-T3 has a porous lid giving a slower (<15s) response time. They require a heater voltage of 4V.

Please note that it is not recomended to solder the sensor connections but to use crimps or some other similar type of connection.

These sensors are small, reliable, simple to operate and can be incorporated in controllers of varying complexity.