Mengtian weighs in at about 20 tons with a length of 17.9 meters and a diameter of 4.2 meters. It will provide space for science experiments with zero gravity, an airlock for exposure to the vacuum of space, and a small robotic arm to support the extravehicular payloads.
source https://www.jagranjosh.com/current-affairs/mengtian-china-successfully-launches-final-part-of-its-three-module-space-station-1667372538-1