The quartz sleeve separates the ultraviolet lamp from the water while passing UV-C into it. Length and diameter both identify a sleeve, and this catalogue stocks several at similar lengths — order against the reactor model rather than against a measurement of the old part alone. The matching lamp is stocked under item 13111-0509 and the sleeve O-ring under item 13171-0912. Wedeco was founded in Herford, Germany in 1976 and is now a Xylem brand.