To provide a fuel filter and a lubricating oil filter each having an exchangeable cartridge for supplying fuel to an internal combustion engine, removing foreign materials from an oil system and separating moisture.

A fuel filter assembly has a base 12 and a disposable filter cartridge 14. A vessel 60 of the filter cartridge 14 performs reception with the base and has a top 58 of an upper area 62 to be fitted to an inner receiving surface 96 of the base which is deformed through operation pressure of a fuel system. Keys or projections 64 which are longitudinally extended are projected from a bottom surface 50 of the base. The projections are selectively determined in their measurements and arranged so as to provide a specified filter capacity, filtering quality and projection matrix unique to the filtering parameter. The projections make corresponding recessions 98 on an upper surface of the top of the upper area when the fuel system is operated for locking the top of the upper area onto the base. The base structure supports the upper area of the cartridge and regulates the extent of deformation thereof.