When looking for an ultra light sleeping bag there’s going to be a great deal of factors. There’s likely to be one huge choice, what variety of fill do you prefer? They have two options for fill, synthetic of down. A synthetic bag is better whenever you’re going to be in an area that’s damp or having a prospect of getting wet because of downs very bad waterproofing. A down sleeping bag is over all a much lighter and warmer fill for per ounce ratings.
If you were to select one for the lightest bag you would have to go with goose down hands down. Temperature rating makes a major difference for weights because the fill rate has a lot to do with your weight. On a goose down sleeping bag a fill rate of 1000 is very warm and a rating of 650 is colder. A synthetic will add much more fiber to insulate you and keep you warm.
Most ultra light sleeping bags have a microfiber shell due to its properties of not ripping easily and being extremely light. This makes for a really good sleeping bag. When on the market for an ultra light sleeping bag the setup that you ought to get all depends how cold you’re likely to be camping. In particular, if you are camping at temperatures that only get as low as 30 degrees a 20 degree bag is the bag to buy.
The perfect setup for weathers as cold as 30 degrees although also keeping extremely light would have to be a goose down sleeping bag with a power fill rating of around 800. This will maintain you extremely warm and can weigh as low as a pound. Good luck finding the perfect sleeping bag for you and remember that synthetics can maintain their warmth even when wet.
You can find more information about sleeping bags at http://sleepingbagsite.com/ease-your-load-with-the-ultralight-sleeping-bag/, where you can read about Ultra Light Sleeping Bag.