Hey, just noticed everyone keeps having questions and problems with their units that they ordered from various places, so i thought id share my experience.
I recently installed a unit for my wifes c class, this is after i had mine in my GLK installed few months prior.
No complaints about this unit, everything works great.
This is not a sponsored review, but guys at 4x4shop.ca are very professional and are actually there to help (there seems to be too many cheap knock offs floating around the web where sellers just flip the unit for few dollars without any knowledge of it or any technical support, and sketchy claims on the units ram HD and android version). the 4x4 guys they seem to sell all over the world and install it them selves at their shop in canada as you can reach them any time during business hours.
Me being inexperienced the first time doing GLK they helped me install it their technical support over the phone/chat and as well as video chat which helped a lot.
Just wanted to share my experience and my honest recommendation that hopefully will save peoples time and money and most importantly sanity of installing and trouble shooting units that they get from else where.
For those interested heres an example of their c class install (thats how i found them through youtube)

Thank you. This is fantastic!!!