Correct size and type of "O" rings for aircon system

[br1anstorm]

I need some quick help with part numbers and 'O' ring sizes. I need to replace the expansion valve and receiver-drier in the (R12) aircon system of my 1990 560 SEC. I have the new parts, but neither comes with new 'O' ring seals for the connecting pipes.

I haven't yet removed the old parts, so can't check the sizes. According to a parts diagram/catalogue I found on the web, the MB part numbers for the 'O' rings for the drier are
140997 1145 - two needed; and
140997 0645.
Then for the expansion valve, the part refs for the 'O' rings are
140997 0845 - two needed;
123997 0340, and
124997 0545.

Can anyone help by telling me what sizes these are, or simply, what sizes I need? I understand that normally replacement 'O' rings come in standard sizes labelled #6, #8, #10 and #12 (are these the diameter in mm?, I wonder).

[Matt L]

The lines are #6, etc. The o-rings are sized based on both diameters, thickness and OD or ID. Some even have a non-round cross-section, but I don't think your car uses them. There is some standardization, but really only because of the relatively few vendors for AC parts.