17-0003 Adapter
WARNING: This page is about a different car, the 2013 BMW X5 M, 2012 BMW X5 M, 2011 BMW X5 M, and 2010 BMW X5 M. However, it is still accessible from the selected car via links, so may be relevant.
0491387 170003 Adapter MW
NOTE:
(Adapter) For screw-on radiator caps (standard thread)/ Series: E28, E30, E31, E32 engine: all, except M51 Free only for motorcycle!!! [Discontinued]
Courtesy of BMW OF NORTH AMERICA, INC.