How light is this bag?
How small does it pack into for trek?
How comfortable is it in below freezing weather?
The bag is 5lbs and rather large. Wouldn't fit in the bottom of my pack even with the compression sack so I bought 3 extra compression straps (like a buck a piece) and cinched it even tighter. That did the trick. Fits fine now.
The bag is warm down to 20 degrees F at least. The collar around your neck is beefy and warm. Zippers big and better than avg. I haven't taken it out in less than 20 degrees yet.
I also have the -20 degree bag for special occasions, haha! It's even bigger and weighs 7 lbs.
This bag is around 5 lbs (maybe a little lighter). Using the compression sack it came with I packed it down to approximately 8x14". I probably could have reduced it more but didn't want to damage seams of the standard compression sack. (I do plan on buying a more heavy duty compression sack for that reason).
The lowest temps I have used it in so far have been the upper 20's. I was more than warm, and in fact had to open the bag one night as I got uncomfortably warm and needed to cool it down. Overall, I would highly recommend this bag. I may never use it around 0 degree temps as we don't see temps that low normally where i am, but i am confident it will do well at least down into the low to mid 'teens.
Bought these for car camping. Not sure on the weight, but it's not what I'd pick for backpacking. I've packed a heavier down bag many years ago, but there are better backpacking options nowadays. You can check out the Alps website for weight and size. Can't comment on the suitability for below freezing as I haven't used it below 40 yet...it was too warm for that.