Neptune Systems Double Junction ORP ProbeNeptune Systems Apex Lab Grade Double Junction ORP ProbeNeptune Double Junction probes will out last most other traditional lab grade probes letting you go longer between calibrations, and having to purchase and replace probes less frequently. The Double Junction isolates the reference gel and probe from proteins and other organics that may otherwise precipitate and clog, shortening the lifespan of the probe. Longer lastingReliable readingsQuality