Calomel reference electrode has a long history. It is a classic reference electrode.
Hg2Cl2 + 2e = 2Hg +2Cl- E0 = 0.2412V vs. NHE 25 C
D.J.Ives and G.J.Janz, "Reference Electrodes," Academic Press, New York,1961�

The electrode is composed of Hg/Hg2Cl2/Saturated KCl solution. It can be inserted into solution directly for general measurement.
For avoiding Cl- ion or nonaqueous solution measurement, it betters to use holder. First, add the solvent and supporting electrolyte into holder, and then set the electrode into the holder. Last, insert the whole electrode into test solution.
It is easy to refill or change the saturated solution of KCl. The electrode is long-lasting
The electrode is made of glass. The electrode liquid junction is made of Porous ceramics .

Electrode length: 105mm (approximate)
Length from joint to bottom: 60mm (approximate)
Diameter from joint to bottom: 5mm (about)Length of holder: 85mm (approximate)
Diameter of holder: 9.7mm approximate)

Price $108 or EUR108