The Bluelab pH Probe is a replacement pH probe (electrode) suitable for use with Bluelab products that test the pH value of a solution.
Unfortunately pH Probes do not last forever as they age through 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 test for hydroponics has a double junction reference which provides a longer life than many other pH probes and is a gel filled non-refillable probe, so apart from cleaning is maintenance free.
Replace only the pH probe, not the whole meter!