\begin{table}%tB.2
  \caption{Correction factors.}
  \label{tab: corr factor}
  %\centering
\small
  \begin{tabular}{lcccc}
    \hline \hline
     Ring & \multicolumn{2}{c}{HALO} & \multicolumn{2}{c}{CXB} \\
     & MOS1 & MOS2 & MOS1 & MOS2 \\
    \hline
    0$^\prime$$-$2.75$^\prime$   & 0.62 & 0.68 & 0.80 & 0.91 \\
    2.75$^\prime$$-$4.5$^\prime$ & 0.74 & 0.70 & 0.70 & 0.78 \\
    4.5$^\prime$$-$6$^\prime$    & 0.63 & 0.65 & 0.89 & 0.95 \\
    6$^\prime$$-$8$^\prime$      & 0.74 & 0.71 & 0.89 & 0.92 \\
    \hline
  \end{tabular}
\end{table}