documentclass{standalone}
usepackage{tikz}
usetikzlibrary{shadows, positioning}
begin{document}
begin{tikzpicture}[node distance=5mm, auto, font=sffamily,
       blockcolors/.style={
        % The rest
        thick,draw=black,
        top color=white,
        bottom color=black!10,
        font=sffamilysmall
    },
    blockheight/.style = {
        minimum height=10mm
    },
    block/.style={
        % The shape:
        rectangle, minimum size=6mm, minimum width=12mm,
        blockheight,
        node distance=5mm,
        blockcolors,
        drop shadow
    }
    ]
node (int1) [block, label=below:too small]{$int dt$};
node (int2) [block, right=of int1, label=below:too big]{$displaystyleint dt$};
node (int3) [block, right=of int2, label=below:just right]{???};
end{tikzpicture}
end{document}