When the probe and sensors are disassembled for routine cleaning, it is important to inspect o-ring for nicks, cracks and damage that may cause leakage. Use this handy kit to replace o-rings as required and always lubricate with the grease provided in the probe maintenance kit. A small brush is provided with a small brush for thorough cleaning of the EC sensor and spare electrolyte for the DO sensor. Proper cleaning and maintenance of your probe and sensors will help ensure accurate and successful measurements!