The brochure for a 2001 5 series indicates an optional "head" side airbag. However, the picture of it in the brochure looks like its only a side airbag without head protection -- only torso level, not neck or head level. Any further infomation on this? I know the "sausage" bag for the front (HPS) is only for the front -- but, is the rear side airbags cover the head in some way?