The CRP-9 is a circular computer of 140mm diameter Circular Slide Rule side is that of the CRP-5. With clear durable cursor for calculation and conversion of Temperature, Time, Distance, Volume, Altitude and Density Altitude, Speed, Weight, Fuel, Endurance, Multiplication and Division, 1 in 60 rule, Compressibility Correction etc. Coloured scales and lettering enhance operation and clarity.