a filter cartridge comprises a length - adjustable end cap attached to an end of a filter body . the end cap includes an annular seal , a spacer coaxially positioned in spaced relationship with the seal , and a connection member including a cylindrical neck in moveable sealing contact within the seal and in a snug sliding fit within the spacer and an imperforate flange including a seal on a radial outer region thereof . a method of joining an end cap to an end of a generally cylindrical filtration medium comprises positioning an annular spacer ring in a recess of a connection flange of an end cap ; melting an exposed portion of the connection flange ; contacting the melted exposed portion of the flange and an end of a filter body ; and allowing the melted exposed portion to cool and bond the filter body to the end cap .