Protective cap for the quartz sleeve — also called a quartz tube — on older Katadyn ultraviolet disinfection systems. The cap closes and protects the exposed end of the sleeve where it leaves the chamber, keeping the dry lamp side clear of splash and shielding the sleeve end from knocks during servicing, which is when most sleeve damage happens. Listed for the older Katadyn range, so check it against the system you hold rather than against a current model. Reference number 1199-0309.