I had made one or two of these some time ago, but they had to be bigger than the original bobbin due to the size of the inserts then available. Things have moved on, and I'm now able to buy miniature USB inserts. These bobbins are therefore the same size as an old wooden cotton reel.
I'm really delighted how these have turned out. What a great gift for a dressmaker, milliner, tailor or textile artist!