Clone trooper Valves

I am looking for the original scale of these valves on the right and left side of the helmet , i think my helmet is a MR cast the hole where the valves should fit in is about 4cm wide and 3,5cm high . do you have any ideas ?

Thanks for the help .
Phil

I'm not sure I follow..... What do you mean by "original scale"?

Ohh sorry , I have a helmetcast without these valves , and I am looking for the scale of these to make them !!

Can you show left side's pic.