WARNING: This page is about a different car, the 2011 BMW 750xi, 2011 BMW 750Lxi, 2010 BMW 750xi, and 2010 BMW 750Lxi. However, it is still accessible from the selected car via links, so may be relevant.
0492471 343000 Holding sleeve MW
NOTE:
(Assembly sleeve) For inserting the piston with sleeve into the tandem brake master cylinder, dual circuit braking system [Discontinued]