Choose a bag that has a temperature rating slightly lower than what you would encounter on the camping days you plan to use. A bag that is 20 degrees F or less is better if you are heading for temperatures near freezing. To allow for more circulation during warmer nights, the bag can be easily vented if temperatures rise beyond your expectations. Sleeping bags can be used up to -40°F. 

You want to choose camping sleeping bags that are light but not compromise safety and comfort. Low weight bags can be more important than other considerations (comfort and durability, convenience, price, etc.). Others consider weight less important than having a spacious bag that allows for good sleep. Bags try to balance these extremes.

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The main decision in fill is between Dura Fiber H1, Dura Loft and Invista thermolite. Invista thermolite Extreme insulation. The outer part of Invista thermolite is made from mini ripstop, waterproof, windproof Cire nylon. Down is the best source of warmth in the woods. This amazing insulation is essentially useless once it gets wet. 

The synthetic fills are more resistant to cold and damp conditions than natural ones, and they have lower sticker shock. Although they are slightly heavier than down and less compressible, synthetic fills trap body heat well. Budget is the main criteria in this economic downturn. 

The cheapest sleeping bags can be found at camping shops or big retailers. The most expensive sleeping bags are down-filled and carefully made. They are well worth the money. High-quality synthetic bags are now comparable to down bags.