What type of 4 & 7 Series are you looking for?
Carbon Dioxide CO2 C4 Infrared CO2 2V Gas Transmitter
Infrared Carbon Dioxide CO2 C4 sensor in 4 or 7 series standard size with integrated analogue 0.4-2.0V transmitter, 0-5000ppm. Optional: 0-1%, 0-2%, 0-5% or 0-30% volume CO2
Carbon Dioxide CO2 C4 ATEx Infrared CO2 2V Gas Transmitter
ATEx certified infrared C4 Carbon Dioxide CO2 C4 sensor in 4 series standard size with integrated analogue 0.4-2.0Vdc transmitter, 0-5000ppm. Optional: 0-1%, 0-