Smaller icon Rated 5 out of 5 stars

To replaced the big icons with the medium sized, so the small toolbars remain small with this add-on, uncommend in chrome/skin/overlay.css the code for smaller icons:

/* Set images used for the small icons */
toolbar[iconsize="small"] #uctb-toolbar-button[disabled="true"] {list-style-image: url("chrome://undoclosedtabsbutton/skin/toolbar-button-small-disabled.png");}
toolbar[iconsize="small"] #uctb-toolbar-button[disabled="true"]:hover {list-style-image: url("chrome://undoclosedtabsbutton/skin/toolbar-button-small-disabled.png");}
toolbar[iconsize="small"] #uctb-toolbar-button {list-style-image: url("chrome://undoclosedtabsbutton/skin/toolbar-button-small-passive.png");}
toolbar[iconsize="small"] #uctb-toolbar-button:hover {list-style-image: url("chrome://undoclosedtabsbutton/skin/toolbar-button-small-active.png");}

This review is for a previous version of the add-on (3.7.1).  This user has other reviews of this add-on.