This very simple option will write the current density as either CHGCAR.new (VASP), job.RHO.new (SIESTA) or fort.200.new/fort.16.new (CASTEP) file. The format in the files of the corresponding codes is kept.
Note that if the charge was cut off from the density (Section 3.6.3.9), the new density (with zeros at grid points that were inside the chosen spheres) will be written.