GroStar Series GS1-P pH/ORP Pen Tester Kit (Gen II) with Replaceable Double-Junction pH Probe and ORP Probe for Hydroponics Water Quality Testing

Apera Instruments GroStar Series GS1-P pH/ORP Pen Tester Kit with Replaceable Double-Junction pH Probe and ORP Probe for Hydroponics Water Quality Testing, Gen II

Apera Instruments AI1108 pH Calibration Buffer Solution Kit for pH/ORP Electrodes, 4.00 & 7.00 pH, 4 oz & 8 oz

Apera Instruments 3M KCL Storage Soaking Solution (8 oz.) for pH and ORP Electrodes