Different versions of oil filler and oil drain plugs
WARNING: This page is about a different car, the 2004 Volkswagen R32. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Oil Filler And Oil Drain Plugs (Version I & II)
Courtesy of VOLKSWAGEN UNITED STATES, INC.
I - Oil filler- and oil drain plug with multi-point socket head
II - Oil filler- and oil drain plug with hex-socket head