Tracks in China are slightly narrower than in Russia and Mongolia, so at the Mongolian-Chinese border the wheels on the trains are changed. Passengers stay inside the train cars while they are raised by huge hydraulic lifts and the wider Russian gauge wheelsets (bogies) are rolled out from under the cars and Chinese gauge bogies are rolled in. All passengers take great interest in this process and the Chinese border guards and rail workers carry out their work with an air of importance.