Flannel Graphite Queen Duvet | Unison | If humans hibernated, we would all own a set of these uber cozy flannel sheets. In versatile gray, they're easy to mix-and-match. And in 60% cotton, 40% viscose of heather bamboo, they're extraordinarily soft. Which means you might want to stay in bed all day - or all winter. Move over, Mr. Grizzly.