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General beginners question:

IN YOUR EXPERIENCE do REI sleeping bag ratings (+20, 0, +40 degrees F) run as advertised?

Know that some companies (Mountain Hardware) are reputed to do better than rating.

Understand and acknowledge the limits of the specified bag rating system - I've read Tom D's (among others) articulate comparisons to the more accurate European system.

For those who will want to know, I tend to sleep cold, and plan accordingly.

Conditions of use are in the Blue Ridge in the winter.

Steadman