Alvin Graduated Beam Compass Item No. 961X Includes two 13" graduated beam bars and one coupling to accommodate circles up to 48" diameter. Inch and metric graduations. Spring-loaded thumbwheel on the top of each slide assembly allows for smooth and precise adjustments. Comes complete with interchangeable ruling pen, pencil, and divider legs. Includes spare leads and needlepoint. Packaged in a protective case with clear cover.