The Refuel Module is a module used for refueling parts that require fuel.
The module is relatively the same size of the Soyuz 2nd Stage. Two orange tanks presumably filled with thruster propellant and normal fuel respectively. Two short red and blue pipe connects them together, and it is all held together with some grey metal bars. It has 1 docking port on the top end.
To use the Refuel Module, one must simply dock it into a module that uses fuel. After successfully docking, switch the fuel valve to connect the two modules tanks, activate fuel transfer for fuel/thruster propellent, and the fuel and thruster propellant inside the Refuel Module will then gradually transfer to the module it docked with. There is enough fuel and thruster propellant inside to at least fully refuel several Space Telescope modules.
If the refueling module is docked with a multiple vehicle structure such as a Space Station, while refueling, if the fuel valves are all open, the module that is being refueled will draw fuel from the closest vehicle docked to it which has fuel.
It can also self-destruct when it isn't docked to anything, which acts as quick junk removal.
The Refuel Module is also used in Mission 10 to refuel the Space Telescope.