My HM1000X makes buzzing noise

My RAW HM1000X makes a low level buzzing sound from fill gauge block area, I removed bottle and replaced fill O rings and bottle O ring and sound is still there, the strange thing is I'm not really losing any air pressure. I have to be losing some air because what else would the noise be coming from ? Next will be replacing the two O rings at ends of V block and gauge.
 
Soapy water revealed small leak from vent hole on regulator housing, when this hole starts leaking air this means seals on regulator are not sealing anymore and need replaced.I removed regulator and replaced metric O ring on regulator body, the others looked fine. Reassembled and no more buzzing sound and no more air venting from hole. I filled gun up to 240 bar and overnight I had no loss of air. I am confident that the gun is now sealed. My Theoben MFR is the same way so I already had a bag of O rings.
 
Soapy water revealed small leak from vent hole on regulator housing, when this hole starts leaking air this means seals on regulator are not sealing anymore and need replaced.I removed regulator and replaced metric O ring on regulator body, the others looked fine. Reassembled and no more buzzing sound and no more air venting from hole. I filled gun up to 240 bar and overnight I had no loss of air. I am confident that the gun is now sealed. My Theoben MFR is the same way so I already had a bag of O rings.

Can you please share the sizes of O-rings for RAW.