def format_wd_stig(wd, stig_x, stig_y):
    """Return a formatted string of focus parameters."""
    return ('WD/STIG_XY: '
            + '{0:.6f}'.format(wd * 1000)  # wd in metres, show in mm
            + ', {0:.6f}'.format(stig_x)
            + ', {0:.6f}'.format(stig_y))