The 1 1/2" needle is mounted on a sapphire-jewel bearing in a fluid-filled housing for minimal needle oscillation. The arrow and compass points are luminous, and for greater convenience, it also includes built-in, free-swinging clinometer needle. It reads any incline accurately to 2°. An engineer’s scale in inches and tenths is on one side of the base plate and a millimeter scale is on the opposite side. It includes instructions. Size: 4"L x 2 1/2"W x 3/4"H; weight: 5 oz.