This Quickbow compass is small enough (6 3/4" long) for everyday use, yet opens to 7 3/4” or 200mm radius so it can be used to lay out the large 14” diameter plates. A well-made thumb wheel and screw mechanism maintains precise adjustment for accurate operation. It has a quick-set, push-button mechanism and comes with a universal adapter for writing instruments and two spare leads. All parts come in a durable plastic storage case.