icon_box – how to get three in a row

Hi,
I am trying to get three icon boxes in a row, but all I can achieve is three in one column … either 4/12th width or 12/12th width. Any ideas what I am doing wrong.

Here is the code

[icon_box icon="hb-moon-lock-2" icon_color="#00a1fd" icon_position="top" title="Site Security" align="center" size="col-4"]

Enter your content here...
[/icon_box]

[icon_box icon="hb-moon-lock-2" icon_color="#00a1fd" icon_position="top" title="Site Security" align="center" size="col-4"]

Enter your content here...
[/icon_box]

[icon_box icon="hb-moon-lock-2" icon_color="#00a1fd" icon_position="top" title="Site Security" align="center" size="col-4"  last_column="true"]

Enter your content here...
[/icon_box]

Thanks.

Graham.