I have no Idea where these things came from, but I use them from time to time. And when I don't, they shouldn't go flying around the junk drawer and never be seen again.

Dimensions:
USB Type A: 12mm × 4.5mm
Barrel Jack diameter: 10.97mm

Inner diameter: 30mm
Outer diameter: 64mm

Note: The cutouts are a tight fit and I had to sand down some of the insides just a tiny bit.