Alvin - Master-Bow Combination Compass with Beam Bar - The Alvin Master-Bow Combination Compass with Beam Bar is a 6 inch compass featuring a rugged gearhead design and interchangeable pencil and divider parts. The Master-Bow Combo Compass Includes a double break leg for precise perpendicular drawing. Easy-to-hold handle adds comfort when adjusting. The Master-Bow Combination Compass rapid adjustment feature creates 1/8 inch to 11+ inch circles. Slip handle for spare ruling pen. 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.