I've got an older model #5 and find it's quite short of the claimed temperature range--their high (comfort) range rating should really be the lower (survival) range number. It's the only bag I've owned that fails to approach the spec'd temperature. The current versions seem better spec'd, so will hopefully perform better than mine.

The MontBell US site seems to have dispensed with their two-temperature rating system, which is probably a good thing. The old system was confusing, to say the least.
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--Rick