Works only on the head size or diameter Really only designed for measuring the head size. Not type such as metric or standard, length, thread pitch, and diameter. If you take a picture of the diameter end, then you can figure the approximate diameter. Cool tech, not really useful.
Bolt sizer Too much room for error
Poor Missized my bolt. 2 trips to the hardwear store.
Awesome Pretty neat for being done by 2 kids.