A filter cartridge for use in separating a hydrophobic liquid aerosol phase from a gas stream and for use in filtering the gas stream; the filter cartridge comprising: (a) a media pack comprising filtration media surrounding an open interior and including first and second, opposite, ends; (b) a first end piece adjacent the first end of the media pack; the first end piece having a first, outer, end surface on an opposite side of the first end piece from the media pack; (i) the first end piece including a peripheral, perimeter housing seal arrangement thereon, which is radially outwardly directed from an end of the cartridge; (ii) the first end piece including a central flow aperture arrangement projecting therethrough in communication with the open interior of the media pack; and the first end piece including a non-circular projection positioned around the central flow aperture arrangement and projecting from the first end piece in a direction axially opposite the media pack; the non-circular projection being positioned spaced from an outer perimeter of the first end piece; and the projection having a shape rotationally asymmetric around a central axis of the filter cartridge such that the projection only fully aligns with itself in one rotational orientation when rotated around the central axis; and characterized in that the projection has a curved side section and an opposite straight side section and further includes opposite straight transition regions or sections (127, 128) extending between the side sections (125, 126). (a) a media pack comprising filtration media surrounding an open interior and including first and second, opposite, ends; (b) a first end piece adjacent the first end of the media pack; the first end piece having a first, outer, end surface on an opposite side of the first end piece from the media pack; (i) the first end piece including a peripheral, perimeter housing seal arrangement thereon, which is radially outwardly directed from an end of the cartridge; (ii) the first end piece including a central flow aperture arrangement projecting therethrough in communication with the open interior of the media pack; and the first end piece including a non-circular projection positioned around the central flow aperture arrangement and projecting from the first end piece in a direction axially opposite the media pack; the non-circular projection being positioned spaced from an outer perimeter of the first end piece; and the projection having a shape rotationally asymmetric around a central axis of the filter cartridge such that the projection only fully aligns with itself in one rotational orientation when rotated around the central axis; and characterized in that the projection has a curved side section and an opposite straight side section and further includes opposite straight transition regions or sections (127, 128) extending between the side sections (125, 126). (i) the first end piece including a peripheral, perimeter housing seal arrangement thereon, which is radially outwardly directed from an end of the cartridge; (ii) the first end piece including a central flow aperture arrangement projecting therethrough in communication with the open interior of the media pack; and the first end piece including a non-circular projection positioned around the central flow aperture arrangement and projecting from the first end piece in a direction axially opposite the media pack; the non-circular projection being positioned spaced from an outer perimeter of the first end piece; and the projection having a shape rotationally asymmetric around a central axis of the filter cartridge such that the projection only fully aligns with itself in one rotational orientation when rotated around the central axis; and characterized in that the projection has a curved side section and an opposite straight side section and further includes opposite straight transition regions or sections (127, 128) extending between the side sections (125, 126).