The exact pipeline used by the Russian soldiers is not entirely clear, although all signs point to it being part of the Urengoy-Pomary-Uzhhorod gas pipeline. Also known as the Brotherhood pipeline, or West-Siberian Pipeline, this was previously used to transport Russian gas to Europe via Ukraine. Partially owned and operated by Ukraine, it has been out of use since the end of 2024.
This gas pipeline, with a maximum diameter of 56 inches, starts at Yamalo-Nenets Autonomous Okrug (Russia) and ends in Zakarpattia Oblast (Ukraine).
...56 inches sounds big, but it is round which means it is 56 inches at it's widest point. Uncomfortably small and the crawling thru it sounds dubious like ya said.

Liberals are like a "Slinky". Totally useless, but somehow ya can't help but smile when you see one tumble down a flight of stairs!