multiple rows for firefox tabs

A while ago when I had to reinstall everything on my computer I couldn't find again which was the plugin that enables the tabs to be shown in multiple rows. When searching in google all I found was a tweak

.tabbrowser-tabs > hbox {
display: block !important;
}

.tabbrowser-tabs tab {
-moz-appearance: none !important;
display: inline !important;
width: 16% !important;
min-width: 16% !important;
max-width: 16% !important;
}   

Actually it's not that elegant. I prefer to use some addon for it. So i found again what I had been using before. It's the Tab Mix Plus, that among several features, enables to show tabs in as many rows as you want:



The configuration for this is a bit hidden. Tools -> Options -> tabs -> Tab Mix Plus Options -> Display -> Tab Bar -> When tabs don't fit width -> Multi- row, and then specify the number of rows you need.