Product review (3 stars): Does what you'd expect, but documentation is scant
These work as advertised, but I found it difficult to find info I needed on the exact dimensions of the parts or the size of the screws needed for the USB connector.

I used these to allow me to install a canopy on the Tarot 650 quadcopter I've been building so that I could see the status light and hook up to the Pixhawk without having to remove the canopy (see photo).

I first searched online for info on these, but found next to nothing. I contacted 3DRobotics tech support, who were very quick in responding but didn't have the info that I needed. I eventually found the specifications for the USB connector online through a parts distributor, and used those to develop templates for cutting and drilling the canopy to install the USB connector (for those that care, the USB connector is an Amphenol MUSB-K152-30, and the screws need to be 2-56 UNC thread, 5.0mm).