FREE SHIPPING! on All Orders Over $99The DownUnder Sleeper Provides All-Season Comfort. Wool is unique: It absorbs moisture. In the summer, you stay cool and dry. In winter, wool is a natural insulator and retains body heat to warm you on the coldest nights. Put the DownUnder Superwash Sleeper on your bed - between the bottom sheet and the mattress—for a better night's rest. You'll sleep more soundly and you'll wake up feeling refreshed.