SUM360LA - Survey Master Compass by Sum 360LA Survey Master Brunton professional series SurveyMaster provides optical quality, accuracy for the tower contractor, engineer, forester, geologist -- anyone needing to determine the height of a tower or similar structure. This unit features: Lubber line for direct azimuth/bearing readings from the side with accuracy to +/- 2.5 degrees Sapphire jewel bearing inside a liquid-dampened vial Aluminum inclinometer card with precise scales for increased accuracy Sine scales (0-45 degrees) Tangent scales (0-45 degrees) Inch and millimeter scales (0-5.25" and 0-125mm) Aluminum body 6.0" x 1.25" x 1.63" / 8 oz