Bluelab Replacement pH Probe for Combo / Maestro MetersBluelab Replacement pH Probe for Combo Maestro Meters If your original Bluelab probe gets damaged or lost then replace it with the Bluelab Replacement pH Probe compatible with Combo and Maestro meters. The Bluelab Replacement pH Probe like the original is fully waterproof, easy to clean and durable thanks to its tough polypropylene barrel. The Bluelab Replacement pH Probe comes with two metres of cable and a suction cup if you want to permanently