Originally Posted By food
A 20 degree bag has these features:

A hood,
Full collar - stops the bellows effect,
Draft tube - zippers cause a draft, and
Baffle construction - not sewn thru.



My Marmot Helium, rated to 15 degrees, has no collar. I'm also not sure about "baffles vs. sewn-thru", as this bag purports to have "sewn-through baffles".

I haven't pushed the limits on this particular bag, but reports are good. I've pushed other Marmot bags, always with happy results.
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