Wedeco reactors with a wiper sweep the outside of the quartz sleeve to remove the scale and film that attenuate UV-C before it reaches the water. A wiper that is worn or wiping unevenly shows as falling measured intensity on lamps that are themselves still good. This is the 48 mm wiper ring. The matching wiper holder is stocked under item 13199-0314 and the wiper rubber under item 1372-1107. Wedeco was founded in Herford, Germany in 1976 and is now a Xylem brand.