The Nauticalia Brass Pocket Sundial is a completely self-contained portable instrument, with a compass for alignment & lid for protection. The gnomon is set for latitudes around 50 degrees North, so will be most accurate in the south of Engl&, northern Europe, Canada & so on. At these latitudes this is a functioning time indicator (in as much as sundials ever were!) diameter 3 inches, height 1 inch. Chunky solid brass.