Extech Ph100 Exstick Ph Meter,H20 Proof,0.00 To 14 - New Open Box 723434132528 | eBay
AquaPhoenix ExStick EC500 Conductivity and pH Meter - EC500
THRENS Water Tester Water Quality Tester Digital pH Meter PH EC TDS Salinity Temp 5 in 1 Pen Meter Precise LCD Digital Multifunctional Water Quality Monitor Test for Aquarium Hydroponics - Walmart.com