Os1 is for 1996-2002 Non-class 2 Non-bose Systems (Plug Like Gwh344) Retains Onstar When Replacing Factory Radio W/aftermarket Radio. Mutes Radio + Plays Onstar Audio Through 2 Front Speakers. All Radios With 21 Pin + 9 Pin Plugs (Door Chimes Are Not Built Into Factory Radio - They Still Work)
