Milwaukee SE220 Replaceable Double Junction pH Probe with 1 Meter Cable and KCL Gel Filled Electrode for measuring pH or ORP in dirty water and solutions with heavy metals or organics Combination electrode contains both the measuring half-cell and the reference half-cell to minimize electrostatic interference and provide consistent readings Epoxy body is impact resistant and durable, and is sealed for minimal maintenance Available in models that measure pH from 0.00 to 14.00 or ORP from +/-2,000 mV Electrode is 12mm in diameter and 120mm long, and has a 1m cable with a BNC connector for attaching to meters with a BNC connection