a filter assembly employs a base which mounts a disposable filter element cartridge . the cartridge includes either a single stage or a dual stage filter system . the base has custom and generic structural members . variations in base design are accommodated in the custom member , the generic member having a generic design . the custom member is molded from polymeric material and requires no additional machining or treatment prior to use . this eliminates filter model specific shop fixtures and gigs , reducing costs and providing greater flexibility .