Our standard 41cm / 16”aeronautical scale rule found in flight schools and pilot bags world-wide, cut from thick Perspex with beveled edges.
The outer edges are marked with nautical miles in 1:500,000 & 1:250,000 scales, on the centre line statute miles and kilometres are marked in 1:500,000 scale.
As part of AFE’s attention to detail, the scale rule is 10nm wide (in 1:500,000 scale) to aid en-route safety altitude calculations.