I have a 1997 E320. i went to the dealer parts guy and asked if there was a P/S pump filter. He says yes and sells me one (part # 000-466-21-04). When I go to replace it, I'm like you - can't see how it would fit. Next I go to the Electronic Parts Catalog the tech's use and it shows two different P/S pumps. One uses the filter. My kind, with the little dipstick, does not. Maybe somebody who works on the cars often can explain?