Abstract: A hollow, cylindrical, resin-bonded filter cartridge has an inner, depth-type filter media with a graded density which decreases (becomes porous) in the radial direction from the inner surface to the outer surface. An outer strip of filter media is then wound in a spiral or helix around the inner filter media. The outer filter media is also a depth type of filter media and has uniform density and is wound with adjacent windings abutting one another such that a continuous groove or channel is provided along the length of the cartridge. The groove or channel provides a greater effective surface area on the outer surface of the filter cartridge. The outer strip of filter media preferably comprises a lengthwise-extending body panel with a pair of leaves extending along either edge of the body panel. The leaves are folded against the lower surface of the outer filter media to provide a multi-layer outer filter media structure.