The Radiometer REF251 Reference Electrode has a glass body, Red-Rod reference system, refillable electrolyte (sat. KCl), double-junction, and porous pin junctions. The REF251 reference probe is recommended for challenging samples or general purpose measurements. The REF251 has a 1 meter fixed cable with banana plug. It can be used with Radiometer MeterLab and Hach Sension+ Laboratory Meters.