Alvin - Basic Bow Compass with Beam Bar - The Alvin Basic Bow Compass and Beam Bar is a 6 inch pencil compass designed with a fiberglass ringhead and pivot design for smooth, firm adjustment. Accurate center wheel adjusts quickly and easily for circles up to 10 inches. The Alvin Basic Bow Compass and Beam Bar has a built-in spindle stop that prevents overextension. Supplied with extra lead, needle point, and T-bolt. This Compass and Beam Bar has a matte nickel finish resists stains and tarnishing. Alvin is one of the primary sources for drafting supplies and drawing equipment in the country. Creative Coldsnow is a pround retailer of Alvin graphic arts, drafting and fine arts products.