R-17D: This 10mV +/- oxygen sensor has a 6 second response time and a 36 month life expectancy in air. This is the sensor used with the “El Cheapo I & II” Oxygen Analyzers and other commercial analyzers such as the MSA Mini Ox, Vandergraph VN202 and Dive Rite VTI Oxygen Analyzer. It is also the sensor used in the CIS-Lunar MK-5 Rebreather. This sensor uses a mono-plug connector and has a hydrophobic membrane.