Guinness drinkers who drink at home will be familiar with the little plastic ball that rattles around in the can after you crack it open and pour out a pint of dark creamy goodness. If you’ve ever wondered what that thing is for, wonder no longer. I’m not sure how I’d feel about it being replaced by a credit-card-sized piece of filter paper, though. Why wouldn’t it turn to mush and make my beer into a cellulose shake?

Bonus: this guy has made a collection of neat YouTube videos about all kinds of everyday technologies and how they work. Here’s one about pop can pull tabs that seems beer-applicable as well.

Cheers!