Apera Instruments, AI1313, LabSen 553 3-in-1 pH/Temp. Electrode for Direct Soil pH Testing, 8-pin, POMFeatures:Proprietary ph. sensor technology and materials from SwitzerlandSpecial LabSen Spear pH sensor tip, ideal for direct soil pH testing. No more slurry making.Pom housing, ideal for use in harsh environmentsPolymer electrolyte - not more clogged junctionLong-life reference system, improving the stability of reference electrode and prolong the service life of the electrodeBacked by proprietary Swiss sensor technology and materials, the LabSen 553 3-in-1 pH/Temp. Spear Electrode/Sensor/Tester is designed for testing soil directly. (This is a replacement probe for Apera SX811-SL Meter) Long-Life Reference System - The LabSen 553 pH electrode adopts a long-life reference system, which is 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 temperature changes. It improves the stability of reference electrode and prolong the service life of the electrode. Polymer Electrolyte - The solid polymer electrolyte makes the electrode hard to be contaminated and maintenance-free. Special Glass Membrane - The LabSen 553 pH electrode adopts a spear sensor tip, which is ideal for directly testing semi-solid samples like soil. Housing Material: POM; Temp. Sensor: NTC 30kΩ; Junction: Ceramic Single Pore; Reference: Long-Life; Electrolyte: Polymer; Length: 90mm; Diameter: 15-6mm; Membrane Shape: Spear; Range: 0-14 pH; Temp. Range: 0 to 60°C (32 to 140°F); Connector: 8-pin; Cable: 3 Ft. Compatible Apera Instruments' meters: PH700, SX823-B, MP511, PH800, PC800. May NOT work with other brands' meters because the temperature unit might be incompatible.