iSpring UVQ55FS is a quality quartz tube that is used in conjunction with the UV bulb UVB55FS in iSpring Whole House UV Water Filter System UVF55FS. This quartz sleeve provides protection against breakage, environment hazards, and temperature fluctuation. Because the minerals in the water slowly form a coating on the quartz sleeve that reduces the amount of UV light reaching the water, it is recommended to clean the quartz sleeve at least 2-3 times a year or replace it every 1-2 years. The package includes a quartz sleeve with two seal o-rings.