Alvin #961B beam drafting compass includes two 13" ungraduated beam bars and one coupling to accommodate circles up to 48" diameter. 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. Alvin beam compasses are quality-made in Germany.