Alumicolor Architect Triangular Hollow Drafting Scale, Aluminum, 12 inches, Purple (3030-3) Hollow scales are lightweight but truly professional with anodized markings in 6 different graduations and an ultra smooth, mark resistant surface. Architect Calibrations are: 16, (1/4, 1/4), (1/2, 1), (3/4, 3/8), (3,1-1/2), (3/32, 3/16)