A four-way precision instrument that measures angles directly between any two planes or any number of planes, such as setting a detachable blade type propeller on an airplane. Snug fitting circles are tooled to close tolerances that minimize the error and play found in other protractors. The circle and plate vial are accurate to 45 minutes per 2 mm. The vernier reads to six minutes. Measures 7.25” base x 7.25” high with a 5.5″ face. Has a matte finish to cut glare. Weight: 2 lbs.