Oakton 12mm Double-Junction Glass Body Refillable pH Electrode, Standard, 0 - 12 pH Range Double-junction to protect silver wire contamination and to help prevent clogging Glass body to resist higher temperatures, and for more effective sealing Refillable for ease of use Annular type junction for faster electrode response Bayonet Neill-Concelman (BNC)-connected combination reference and measuring cell, for ease of use and to provide tight coaxial cable connections