This 4” Clinometer Compass is an instrument for measuring angles of slope (or tilt), elevation or inclination of an object with respect to gravity. A sighting arm folds out and readings are taken with a magnifier. When the lid is closed, it presses a mechanism that locks the needle. Under the cover a mirror is used to take a reflecting reading. The brass dials are inscribed with 2 sets of scales. This compass measures 4” wide x 4” deep x 2.5” high and weighs 2 pounds. This compass is a beautiful asset and will compliment the nautical decor in any room in your home, office or cabin, not to mention being a perfect nautical gift.