Casper Down Duvet Insert & Comforter All of all the new cooling duvets, I decided on the Casper Down Duvet Insert & Comforter ($249-$349) because I love down bedding. The lightweight choice has a fluffy, yet soft feel that doesn't overheat me. Image Source: casper.com Casper Down Duvet Insert & Comforter $249 from casper.com Buy Now