Kelty Camp & Hike Cosmic Synthetic 40 Deg Sleeping Bag Duffle Bag/Smoke Regular 35428820RR. While we can’t take the pain out of yKelty’s elevation gain we can put you on the trail with the new Cosmic Synthetic sleeping bag. It’s a fully equipped mummy bag that’s light on weight and yKelty’s wallet. The Cosmic Synthetic is a three-season superstar built with Kelty’s new Cirroloft synthetic insulation for lightweight compressible warmth. Soft-as-silk nylon taffeta fabric means you’ll be thinking less about weary hiker feet and daydreaming about more QT in the outdoors.