Marine adventurers who need a sighting compass choose the Suunto MCB Compass. The Suunto MCB floats and features a mirror that locks at set angles of 60, 120, and 180 degrees. Mirror compasses allow you to view the compass dial and background at the same time. Plus, the vertical line at the center of the mirror can be conceptually extended to the horizon, which helps you to more accurately target bearings. Use the attached whistle for signaling.When taking readings, the notched rotating bezel turns easily and in 2 degree increments. The clear plastic base allows you to see maps and charts beneath the compass. The map scale displays in inches and millimeters.