SRX-MA333-M PPM Oxygen Sensor replaces AII Model GPR-12-333-M PPM oxygen sensor. Sensor is designed with an integral aluminum housing and screws directly into a sensor housing with M16 thread. It is a galvanic type micro fuel cell specific to oxygen. Its innovative design with electro-etched sensing cathode provides with extremely smooth sensing surface for excellent signal stability, very low noise and drift. Proprietary electrolyte formulation enhances sensor performance at extreme ends of recommended operating temperature range. Sensor is designed, developed and manufactured in the USA.