Models 389VP and 399 VP sensors have been added to the company’s line of sensors. The Model 389 VP is housed in a molded Tefzel® body with viton O-rings, and does not require electrolyte replenishment. Model 399 VP is a disposable pH/ORP sensor housed in a molded Tefzel body with 1-in. NMPT threads suitable for insertion, submersion, or flow-through installation.