This is a premium sleeping bag for cold weather.

It is filled with 900 ci fill power down, and has a very lightweight shell fabric.

Here are the important things you need to know about this sleeping bag:

Weight and bulk: My Lithium bag weighs 2 pounds, 7 ounces (weighed on my kitchen scales.) That is extremely light weight for a winter bag. The bag also packs down to a very very small package when stuffed (not much larger than a football.)

Temperature rating: Marmot rates this bag at 0 degrees Fahrenheit. I am a cold sleeper, and I have found this rating to be conservative. I have slept in this bag in sub zero temperatures and have been comfortable. Furthermore, unlike many ultralight sleeping bags, the Lithium is cut large enough on the inside so that you can wear warm clothing inside the sleeping bag without undue constriction. This allows you to push the comfort rating of this sleeping bag well into the sub-zero range.

Comfort: As I mentioned above, this sleeping bag is cut with ample girth and inside room. I weigh almost 200 pounds, so I'm no anorexic waif and I still find this sleeping bag to be plenty roomy, even when wearing extra clothing. The collar and hood are well designed and form a nice snug closure without strangling you. Furthermore, your face doesn't come in contact with scratchy velcro. To save weight, the zipper is only 1/3 length, but that's not really much of an issue in a cold weather bag, as you are seldom in a situation where you need the extra cooling and ventilation of a full length zipper. The zipper has a stiffened anti-snag tape sewn in behind it, which prevents dreaded zipper snag.

Miscellaneous performance: The fabric is super lightweight, but quite water resistant. I've used this bag in snow caves, and the fabric has shrugged off the inevitable minor water drips. It is a down bag, so it has all of the shortcomings that are inherent to down, mainly sensitivity to water. Unlike a synthetic bag, you can't jump in the sleeping bag with soaked clothing and dry out overnight. You have to be careful to keep the bag dry, particularly on long trips. If you are using this bag for multi-day trips, it's a good idea to dry it in the sun when possible.

Overall conclusions: I own a number of cold weather sleeping bags. Because of the light weight and low bulk of the Lithium, it has become my bag of choice for winter camping. In winter, your pack tends to be bigger than you want it to be because of the warm clothing you have to carry. This sleeping bag helps trim my pack down and keep the load size reasonable, which is particularly nice when skiing. After many nights of use, I can say that this is a terrific winter bag. Keep it dry, and it won't let you down.

Recommended: Yes