Quick-Release Coupling Adapter For Service Connections
WARNING: This page is about a different car, the 2010 Volkswagen Passat and 2009 Volkswagen Passat. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Quick-release Coupling Adapter For Service Connections
Courtesy of VOLKSWAGEN UNITED STATES, INC.
High-pressure side, nominal size 16 mm
Low-pressure side, nominal size 13 mm
NOTE:
This quick-release couplings are delivered with the service station.