This electronic chart measurer can be set to work on any map, chart or drawing. It displays distances on a large LCD in nautical miles, kilometers or statute miles.It has nineteen built-in scales from 1:10,000 to 1:5,000,000, and has 3 user createable scales; and an automatic scale for charts without scales, but where some distance is known. A pleasant chirp lets you know the wheel is moving and not slipping. Power is from 2 AAA batteries (included). A durable plastic protective case is available. One year warranty. SW 1 lb.