Its a cheap ebay chinese unit with no brand, initially I was going to get a branded one but prices are ridiculous. I went to the states on holiday and named units were more expensive so I gave the ebay unit a go after reading a few reviews.
It has, usb, ipod connection, gps and two sd slots (one for sat nav), steering wheel connections, sub connections.
As for fitting it, it is straight forward and cheap, as the golfs double din space is too big you need a plastic adapter £25-35 (plenty off info on it if you search). I did a bit more, I put in another fusebox in for future add ons £12-15, fed a seperate power source from the battery in and fitted a rocker switch to kill power. Followed by an aerial adapter £3 due to the unit having a different antenna socket.
As for the unit I have had it about a year now and I am chuffed with it, sound quality is average, but the sat nav function is very good, it also allows use off didferent software, I had tomtom on there which was a fiddle, but in the end I went with iGo8 which imo is the best gps software which is what I had on my phone.
As I am on my phone, I just did a quick search off what I posted in the past, so check it out and the links:
Cheap ebay one?
Think I was meant to post this up a while back, but banburyCo also did a similar job using a cheap ebay double din (his face comes off, mine doesn't). Mine has sat nav, camera inputs, Ipod adapter aux-in etc... Fitted easily and cheaply. There is a thread here when banbury did his install, but I talk about mine abit as I installed my unit prior to his.
http://www.golfgtiforum.co.uk/index.php?topic=158309.10
Also s-l-i-x below in background spying on two birds undressing down by the river 
(using iGo8's speedo and altitude)
