The Extech PH105 pH ExStik® Electrode Module is an easy to clean, rugged flat surface pH electrode. It is interchangeable with the ExStik® Chlorine or ORP meters and measures in liquids, semi solids and solids. Also, it has the ATC via the built-in PT-100 Ohm sensor. The Extech PH105 pH ExStik® Electrode Module comes complete with the protective connector cap.