Filter with Variable Cross-Section Axial Seal

Filtration systems having filter elements having an axial seal member with a variable cross-section are described. The variable cross-section is matched by the non-planar sealing surfaces of the housing and housing cover that receive the filter elements. The non-planar sealing surfaces of the housing and the housing cover prevent proper filtration system function when an unauthorized replacement filter element having a flat axial seal member is installed in the housing.