This replacement ultraviolet lamp is for the 12 gallons per minute ultraviolet water filtration system. This lamp is used in a ultraviolet purifications source which is enclosed in a protective transparent sleeve. The lamp is mounted such that the water passing through a flow chamber is exposed to the UV-C light rays. It is essential that you change your ultraviolet lamp annually. The ability of the lamp to emit ultraviolet light decreases over one year in operation. This lamp is rated at 9000 hours of continual use.