How do I choose the right membrane cartridge for my sensor? Download FAQ Membrane Cartridge Selection If your sensor cathode looks like this Broadley James OxyProbe II Broadley James OxyProbe Broadley James OxyProbe Mettler Toledo® Ingold® Mettler Toledo® Ingold® Mettler Toledo® Ingold® Use this membrane cartridge model OxyProbe II OxyProbe (12mm) OxyProbe (25mm)