I bought an adapter to charge my usb devices in my camper. I looked for a place where to install it and decided to replace a standard 12 V socket. Now I needed a new cover to make things fit together. Luckily I had a new 3D-Printer ans so I made one of my first 3D-designs with freecad. I added the tube in the center, because the space behind the cover was not deep enough for the installation. The ring on the backside gives stability to the cover plate.Needs support underneeth. I added the freecad files, so you can customize it. This is the converter I bought - others work as well! http://www.amazon.de/Dual-USB-Zigarettenanz%C3%BCnder-Adapter-Handy-Deckel/dp/B00JFTAJ4E/ref=pd_bia_nav_t_1?ie=UTF8&refRID=1CBKNZ2WXKDWJ64Y67CV