u/ImportantCharacter55

I have a question about sizing and I’d really appreciate some help.

I own an unissued GP-5 gas mask in size 4, and I’m thinking about getting a brand new Czech CM-3. The issue is that I haven’t been able to find clear information online about CM-3 sizing.

I did find one listed for around €20 / $23 in size 4. I also came across a Reddit post showing CM-4 sizing, but I’m not sure if that translates to the CM-3 system or if it’s useful for comparison.

Given that I already wear a size 4 GP-5, would a size 4 CM-3 likely fit me as well, or do the sizing systems differ significantly?

Any advice or experience would be greatly appreciated, thanks