The Weems & Plath Compute-A-Course is a compact, multi-purpose plotting tool ideal for general boating or commercial use. The Compute-A-Course can be used for position fixing, course plotting, and distance measurements with the included scales. Using the log scale on the instructions, time/distance calculations are a snap. The Compute-A-Course is packaged with instructions in a reusable zip lock storage bag. Dimensions: 7-3/16" w x 8-1/2" h.