After prolonged use, residue and filmy deposits may build up inside the Sludge Judge®. The cleaning brush used with a mild detergent and warm water will help break up these materials and keep the unit clear so accurate sludge readings can be taken. It is made of galvanized steel wire and polyester bristles. The brush may not be able to clean oil and grease - see the cleaning rod for this application. Disassemble the unit and clean each section separately. Use for Sludge Judge® and Sludge Judge® Ultra. 6 ft. (1.83 m) L. 1 in. (2.54 cm) diameter bristle.