That's the Fellow Prismo, which prevents drip without inverting and also adds a little pressure (AeroPress have also recently released the Flow Control cap which aims to do the same but is apparently not as reliable). I don't trust myself to try inverted. I got a Prismo after I left my filter cap at a B&B and the first coffee shop I went to didn't have spare caps but did have Prismos. Never looked back. I add a regular paper filter above the Prismo's metal filter so the coffee is less muddy. I've also rediscovered Fellow's "espresso" recipe for the Prismo which does come kind of close to real espresso.