The sensor holder positions and seals the ultraviolet intensity sensor into the reactor wall. Holder length sets how far the sensor window sits into the flow, which makes it part of the measurement rather than a mounting detail — a validated reading depends on the correct holder as much as on the correct sensor. This is the long holder supplied for retrofitting the ME series. Wedeco was founded in Herford, Germany in 1976 and is now a Xylem brand.