A replacement probe for Bluelab Combo and pH meters and Guardian monitors The Bluelab pH probe is a replacement pH probe (electrode) suitable for use with Bluelab products that test the pH of a solution. Unfortunately, pH probes do not last forever as they age with normal use and will eventually fail. With good care and use (keeping the probe tip wet and cleaning once a month) you will extend its life. The Bluelab pH probe has a double junction reference which gives a longer life than many other pH probes and is a gel filled non-refillable probe so apart from cleaning it is maintenance free. Replace only the pH probe, not the entire meter! Easy to cleanGel filled (non-refillable), low maintenanceDouble junctionWaterproof cable jointProbe holder included - keeps the probe safeQuality BNC connection2 metre standard cable