If you see one for sale in a bag or carrier it has already been opened and likely issued (even if never used). These hard plastic shells are how they were produced so the mask didn't get a fold or crease from improper storage. S mask is brand new in the factory clam shell, never issued. Pics of mask outside clam shell are for an example, yours will be unopened and the listed size. Standard 40mm NATO canister thread.These are better for folks that aren't used to wearing a mask, they were designed for support troops and comfort for all day wear while working. Less rigid and the large field of view helps keep claustrophobia down.
Small is your only option for children and obviously small adults, if in doubt a smaller mask can work but to big = leaks. The item "MCU-2p Gas Mask Small Respirator NEW in clam shell" is in sale since Tuesday, March 24, 2020. This item is in the category "Collectibles\Militaria\Surplus\Personal, Field Gear\Gas Masks". The seller is "triumphrat675" and is located in Fayetteville, North Carolina.
This item can be shipped to United States.