TETRA UV REPLACEMENT Quartz Sleeve ( UV2 ) ** Manufacturer recommendation is to service your filter once every year to year and a half ( 12 - 18 months ) Service PLS18 Tetra Greenfree UV2 4400 Brand NEW in the BOX INCLUDES: ONE - TETRA UV REPLACEMENT Quartz Sleeve ( UV2 ) A UV Filter will lose its effectiveness if you do not regularly service the components. This can result in green pond !