A circular disk covered in rubber or plastic with a hole in the center where the edge is sometimes tensioned by a spring that prevents fluid from leaking at the Engine Oil Filter Housing. Engine Oil Filter Gasket. Engine Oil Filter Housing Cover O-Ring. Engine Oil Filter Housing O-Ring. Cover O - Ring. FLTR Cap (O RING). Gasket. hsng. Included with: Filter assembly, Filter Housing, Oil Filter, Oil Filter assembly, Oil Filter Housing.