These electrodes are a METTLER TOLEDO success story! With their open junctions these electrodes are particularly insensitive to contamination. The polymeric reference electrolyte XEROLYT® on these sensors is in direct contact wit the measured medium, hence there is no junction to block. The PEEK shaft is both chemically and mechanically extremely resistant. The new SteadyForce™ electrodes are brilliant: The reference system is under over-pressure, guaranteeing electrolyte discharge. The constant but controlled gradual discharge of electrolyte by the ceramic junction ensures extremely reliable and reproducible results. 2-in-1 refers to a reference and pH half cell in one. 3-in-1 refers to an electrode with a built-in temperature sensor as well as a reference and pH half-cell.