SRX-CT21 oxygen sensor is for industrial process gas analysis that demands a quick response. SRX-CT21 is a drop-in replacement toTeledyne Model B-1, B-1C, Analytical Industries PSR-11-21 and PSR-11-213 % O2 sensor. T90 response under 6 seconds, expected sensor life is 9 months under ambient temperature and pressure. Sensor is designed, developed and manufactured in the USA.