It is a large module with 4 docking ports used for building the ADS. Air cannot go through this module because it is filled with circuits and wires to and from the docking ports, and thus has no room for air to go inside.
This part uses 9 units of Power.
- Despite it looking similar to other habitable modules, air cannot flow through this part.
- Also, this module does not have any space for Cargo, unlike the habitable modules it looks similar to.