2007-2013 Audi TT RMK (Radio Mounting Kit) List of all products for your TT
For Double Din radios use this kit. RMK5-TT2
This is a great writeup for installing a doubledin unit in your vehicle.
http://forums.mwerks.com/showthread.php?7114688-Installing-Alpine-ILX-007-CarPlay-head-unit-into-the-TT-custom-ashtray-dock-for-iPhone-6