Get Schooled In The Geometry Of Comfort Remember the trapezoid from 10th-grade geometry? Turns out, this funky ol' shape is ideal for helping sleeping bag baffles retain heat. The trapezoidal baffle construction improves on our best-selling Cosmic sleeping bag-and it's just one of the reasons the Kelty Cosmic Down 0 is still our favorite three-season superstar. We also love the natural-fit foot box for happier feet, and a PFC-free water-repellent coating for a healthier environment.