Model SRX-CT17A oxygen sensor is specifically designed for measuring oxygen in automotive exhaust. Fast response from air to 0.1% in under 30 seconds. SRX-CT17A is a drop-in replacement for Teledyne R-17A, Part Number C43690-R17A, Envitec 00A101-1, City Technology AO3 and IT Gambert A-O2. Expected sensor life in air is 44 months. Proprietary electrolyte formulation ensures full utilization of Pb anode, thus providing longer life without signal drift and minimizing periodic calibration requirement. AST brand sensors are designed, developed and manufactured in the USA.