Minimum 20-year service life. Available in three models: Cu-CuSO4, Ag-AGCl, Zn-ZnSO4. Color coded for quick and easy identification. Special porous ceramic contact plugs allow removal and re-entry into liquid without damaging the electrode. The unit is thus reusable and may be reactivated (after use) for a period of up to one year. Technologically advanced “ion trap” prevents contamination of Cu-CuSO4 electrolyte. High-impact resistant plastic electrode case will not deteriorate even in highly corrosive environments. Complete installation instructions included.