\begin{table}%t3
\caption{Comparison with previous studies for common BL Lacs.}
\label{compbl}
%\centering
\par
\begin{tabular}{llllll}
\hline
\hline
Object & $R_{\rm e}$ & $M_H$(gal) & $R-H$ & $\Delta$($R-H$)/$\Delta$(log $r$) & Ref.\\
(1) & (2) & (3) & (4) & (5) & (6) \\
\hline
MS 0158.5+0019 & 12 & --26.0 & 2.1 & --0.22 & This work\\
               & 4.7 & --26.3 & 3.3 & --2.0 & C03\\
PKS 2254+074   & 13 & --26.5 & 2.1 & --0.75 & This work\\
               & 32 & --25.6 & 1.8 & 0.10 & K98\\
MS 0317.0+1834 & 6.8 & --25.5 & & & This work\\
               & 14 & --25.2 & & & Wright et~al. (\cite{Wri98})\\
\hline
\end{tabular}
\end{table}