Abstract: A core extender and seal are provided which may be used in combination with cartridge filters. The core extender includes a body having first and second ends which are connected by longitudinal communication means through the core extender body. A radially extending shoulder extends from the body and is axially spaced from at least one end of the body, and preferably is a flange having on at least one lateral surface thereof an annular sealing ring. An external surface extends from at least one end to the radially extending shoulder. The portion of the body defined by an external surface may be inserted into the longitudinal bore of the filter cartridge in order to perform a sealing and connecting function between adjacent filters or a cartridge filter and the filter housing.