It all depends on how warm you want your comforter to be. Our favorite options from testing had fill powers around 650 to 700, though those who sleep hot might want to shop for a lighter fill power of around 500. The higher that number, the better your comforter and its fill will be at insulating you while you sleep.

Goose down is considered the best filling for a comforter, but even then, there are more specific kinds of goose down. Siberian, Hungarian, Polish, Canadian — you’ll see several terms thrown around when shopping for a down comforter. Our advice is to worry less about what kind is best and look more closely at two variables: the source and the filling percentage. Do you know where the down is coming from? Is the filling all down, or are there other materials within? If you have answers to those questions, you should feel confident in what you’re getting.

No. Some of the down comforters we tested don’t even come with corner loops or tabs for attaching a duvet cover, and several of our contenders are available in colors that look great on their own. That said, if you want to keep your comforter particularly clean, or if you prefer the feel of a different material like flannel, a duvet cover can make a big difference.