I bought this whoopie pie pan on sale from Williams-Sonoma, because I wanted to make small tartlets without having to wash a bunch of miniature pans. It has an excellent nonstick surface and is heavy/thick enough to promote even heat distribution.
I already have 4" tart shells and a muffin-top baking pan that also has 4" wells. But I find this size portion a tad large.
The 2¾" diameter of the whoopie pan wells yields portions half the size of the 4" ones, which is ideal if you want "just a little" dessert.
I think it would also be good for making a baked version of blinis and other hors d'oeuvres. A nice addition to my equipment arsenal. I also have mini-muffin tins but they are a smaller diameter, and deeper, than this pan's wells.