I've been using containers since they first came out. I totally love this. I can isolate my banking and financial activity on a Banking container tab, and keep my work activity kept inside a Work container tab. Nice.

The only thing I'd been wishing for was that I could have a default tab assigned for when I open up Firefox.

The beauty of this add-on, is that I can assign containers to specific websites, and every time it comes up, I no longer have to click on a URL then either move the URL to a container tab already opened (default is no container), or open FF and open a container tab, then paste in the URL.

Now, when I go to a bookmark, it's one & done. You even will get a message for one you've recently assigned a tab, asking you if you want that to be the default tab for it. Perfect. Highly recommend this as well.