Is a scale with which you can calculate the effective average pressure of the ships main diesel engine with the indicator card easily and accurately. The addition of P1 + P2 .... P10 on the indicator card can be read more quickly and precisely by simply sliding the transparent 3 slides on the indicator card. The size of the scale plate is 130 x 200 mm. This unit is made of plastic and is light, compact, and easy to handle.