Sit your HTC One X just above the screen for the radio on a Hyundai i30, actually rests on the slot for the CD. Back is large enough to stick on a NFC tag to ensure the right app starts, volume is up and bluetooth is active.Print both pieces. Nobs on hook will line up with holes on the back of the holder. Find the ideal nob hole combination for your car and your desired viewing angle. Superglue together (falls apart regularly if you don't). Optional 1: I got a bit of sugru and stuck it to the rim at the back/bottom that sits in the cd slot. This will remove some of the rattle you get from plastic on plastic. (Rattle are a pet peeve of mine). Optional 2: Stick a NFC sticker on the back. Install appropriate software on your phone (I used "NFC Task Launcher", in the play store). You can get the stickers in lots of places, in the USA you can pick them up from Adafruit, here in Australia I got them from littlebirdelectronics.com.au.