Instruction: Extract information from the supporting document to answer the given question.

Input:
Question: how big of a hole do you need to drill to flush-mount the adaptor?
Document: Drilled a hole in my dash. Unplugged the Pioneer USB cable, which was working fine. Plugged in the Xtenzi. The music was distorted and garbled. Plugged back in the Pioneer cable and all was well again. The Pioneer USB cable works fine but I wanted the &#34;clean&#34; look of a dash mount.I've processed a replacement and hope it was just a bad draw on the first time, and not cheap cable with a big price tag.
I didn't use the supplied mount but instead cut a hole in the dash of my 94 YJ. Form/Fit/Function is great. I'm happy with this.
I have not installed this yet, however I received it faster than expected and the product looks just like it's described. Great to have the option to mount this on the dashboard if you don't want to drill into your instrument panel to make an opening.
Purchased this for a use other than as intended, I have a studio production desk where the CPU is a bit hard to access, this allows me to mount a USB and headphone jack underneath the front edge of my desk, perfect for quick plugin of a set of monitors.
This extension cable works great. It fits perfectly in a cigarette lighter mounting hole. It is made out of a sort of rubberized plastic, not the typical cheap hard plastic you would expect. Very well made!
The item is as seen however in reality it's a bit bigger than I expected and that would make it a bit harder to fit in a car. The diameter is wider than expected and seems bigger than the standard lighter socket. The depth of it is quite long and the bracket is large to accomodate it. This would be ok in a truck, caravan or bus but in a small car it's just too big. If there was an equivalent smaller sized unit I would have bought that.
For $30 USD I expected quite a bit from this item. It has failed to live up to my expectations. Whenever you try and mount it, the nut on the back just backs off. I would not recommend this product. It is a good idea, just poorly executed. I was expecting something with the quality and mounting ability like thisBlue Sea 1011 12V DC Socketnot something flimsy and cheesy.
When installed, it actually sits around 1/16&#34; off the face of the hole. However, It's not really noticeable unless you're actually looking for the gap.The other thing that I did not like were the threaded nuts to secure it to the mounting surface. They're actually made of rubber instead of metal or hard plastic, so it's kind of a pain to tighten the nuts.
I bought this to connect to a Pioneer AVH-X4500BT receiver in my 2005 Silverado. I replaced one of the two existing 12V receptacles with this and it looks nearly like a factory install. I left off the dust/moisture cap since this is inside of the cab and not exposed to anything that would potentially damage it.The install required no cutting of the existing 12V receptacle hole which was excellent!
I was looking for something that would fit in the existing hole for standard 12V power port in a car. This fit perfectly and looks like it belongs there instead of something that was added later. I would have given it 5-stars but the nuts are hard rubber instead of plastic. The softer material makes it difficult to get it tight to keep the thing from spinning but it can be done. I would definitely buy it again.
Answer: The threaded part is 28mm wide, the top of the unit is 33mm wide so you only have a 5mm lip.