Please note, this is NOT for the Hard Disk based COMAND (with built in phone/linguatronic) in MY2009 onward cars.
The ML/GL/R class units are slightly more advanced than the A/B/C/CLK units as they have an inbuilt Compass function, and an extra 'rear' auxilary input for the rear entertainment system DVD player.
It is an invaluable tool to get the most out of your new navigation system.