These are 90° isosceles protractor triangles with lifting handles for easy positioning on the chart. The legs are 8 inches long. A millimeter or inch scale is printed on the top edge (hypotenuse). Construction of the deluxe model (Linex #2800MH) is of heavy gauge plastic (.107 inch). Construction of the standard model (C-Thru MT-78) is a lighter gauge (.058 inch).