A secondary filter cartridge radially nested within and radially supported by a main filter cartridge. The secondary cartridge has a flexible multi-leg crown “with slits” which engage a receptacle of the main filter element for radial support and a central pin projection interior to the crown extending outwards to protect the crown from impact damage. The main filter cartridge bottom end disk has axially extending, spaced apart projections engaged into matching pockets or gaps provided between engaging inward projections on an interior end face of the filter housing, rotationally fixing or locking the filter housing and the main filter cartridge. The main filter cartridge includes an anti-rotation housing engagement member extending through a filter housing wall to the exterior indicating presence of a properly installed filter cartridge and rotatably locking position of the housing and main filter cartridge.