Beam compass by Alvin 961B beam compass features two 13" beam compass bars create circles up to 48" diameter. The Alvin beam compass is makes it easy to draw circles and ellipses to the desired size. The beam compass by Alvin has interchangeable ruling pen, pencil and divider legs included. The beam compass also includes a small tube with spare leads and needlepoint. Comes complete with case Alvin beam compass.