Here’s a problem and a solution all in one post!
The screen-accurate gas mask hose that connects from the air bladder behind his head to his mask is actually a combination of two different types of hose. The light grey hose is from a PDF-D childrens’ gas mask and is more flexible, which was probably done on purpose to make it easier for the actor to move his head about. The black hose is the more standard type of russian gas mask hose you frequently find on the Soviet GP-5 or M41M masks. These hoses, stock, actually screwed together without any problem when I bought them, but the threaded metal connection between the two hoses was huge and didn’t look anything like the screen version.
In an effort to solve this problem, I modeled and printed my own connector. I disassembled the hoses and removed their original clamps, and designed this part so that the hoses would stretch and simply slide on and over the flared ends on either side. You could then tape them or wire them for a tight seal, but I’ve noticed it isn’t actually necessary.