When you grow up in the USA, all you know when it comes to measurements is the imperial measurement way of doing things. Quarts, gallons, miles - the whole nine yards. See what I did there? Thru the years, the USA has tried to convert society to the metric system only to see failure. Anyway when I got into this 3D thing, I was pretty much forced into the entire metric way of seeing things and quickly found it hard to visualize what a millimeter “looks” like. I needed something I could feel in my hands and this gadget was born. At least now when I am thinking in designing that some part should be about a quarter of an inch thick, I can pull this thing out and design it close to 6mm without have to get more precise later on in a final version. Guess it's hard to teach an old dog new tricks as the saying goes. Just maybe it will help someone else along the way…