Compressibility
The Klymit KSB 20 utilizes 650 plus duck down and a 20 D nylon shell that compresses well. The amazing stretch in this bag helped with packing it into a compression bag.

Warmth
The KSB 20 has a manufacturers rating of 20 degrees F, but does not differentiate that as a comfort rating or a limit rating. I found the KSB 20 to be warm in temperatures between 25-35 F. I did get cold on nights below 25 degrees F and had to add clothing to be able to sleep. The hood of the KSB 20 has a good fit and is comfortable, but as I tightened it down, I could feel the string in the hood on my forehead and around my head. 

Features
The Klymit KSB 20 comes with 650 fill duck down, a 20 D Nylon shell to protect the bag and a small storage pocket on the inside of the bag, which was big enough to store a headlamp, but nothing else. I wish it was big enough to store a camera, iPhone or other items with batteries to help protect them in colder temperatures. 

One of the best parts of this sleeping bag is the stretch baffle system, as the horizontal sections are sewn with elastic thread making this bag “Super Stretchy.” An oversized foot box added to this comfort and allowed me to actually stretch tired muscles inside the sleeping bag. To say this bag allows you to move around easily is an understatement. The breathable shell fabric helped reduce condensation and dried quickly when condensation was present on the shell. 

Overall Comfort
The KSB 20 has more stretch than any bag I have tested. This really added a lot of comfort to the bag, allowing me to stretch out, move around and never feel encumbered. The 650 fill down is fluffy and comfortable and while I found the bag to be warm, the 20-degree F rating is a bit aggressive. 

Durability
The Klymit KSB 20 proved durable even after weeks of serious use. The zipper performed well, aside from occasional snagging, and the shell handled tent condensation well.