Casper Casper is known first and foremost for its mattresses, but it has also expanded into making bedding products like sheets and pillows. I tried a selection from its Cool Supima line and was rewarded with a comfortable sleep experience: The cotton sheets are cool and crisp, the duvet cover is weighty and well-designed, and the pillow is soft yet supportive. From a mattress-first company, the bedding is impressively good and offered at a reasonable price, too. In addition to Cool Supima, you can shop Linen and Cotton options. Right now while supplies last, Cool Supima sheets are up to 40%