Made from laminated plastic. Calibrated to the following:1" = 660 ft. = 1/8 mile. 1" = rod; 1" = 440 ft. = 1/12 mile; 1" =10/tenths. Central area has equal dotted squares. 1 dot = 0.1 acre; 25 dots = 2.5 acres; large square = 10 acres. Dimensions: 6-3/8" x 2-1/2".