Built with proprietary sensor technology and premium materials from Switzerland, Apera LabSen 553 PVC-body pH/Temp. Electrode is designed for direct soil testing and soil slurry testing. LabSen S-type spear glass membrane - low resistance and high firmness, rendering fully stabilized readings in 15 to 30 seconds, and is yet 10 times stronger than traditional glass membranes, highly resistant to general impact, eliminating the chance of accidental breakage when inserting into the soil. Open&Ceramic double-junction with Polymer electrolyte - ensures full contact with test samples while minimizing junction clogs. No need to refill electrolyte. Long-Life Reference System - composed of a glass tube, AgCl, and a reference silver wire. The top end of the slim glass tube is stuffed with cotton, which prevents the reaction between AgCl and electrolyte when the temperature changes. It improves the stability of reference electrode and extends the service life of the electrode. Compatible with all Apera Instruments meters with BNC and RCA connectors such as PH910, PH9500, PH850, PC8500, and PH820. May NOT work with other brands meters because the thermistor might be incompatible.