I wanted to put this review out due to the bag not having many. 1st - the where. I was in Colorado for 2nd rifle from the end of October until mid November. We slept at 7800 for a few nights averaging low 30's, we slept at 11k for a few nights averaging in the 20's and then dropped back to 8k for a snowstorm which the weather averaged the teens at night. Now I want to preface that I did have a r4 rated mat and a 4 season tarp over the top of me pitched as low as possible. That r4 mat probably helped more than I know, but what I will say Is I never woke up cold. The bag gave me concerns at first because the down gets cold just like a blanket on your bed, but let me tell you when zipper is up the heat soaks in and holds within minutes. I purchased the xl because I have a wide chest and I had plenty of room, to move and roll with minimal sleeping bag pull. I don't like to feel restricted and I never did once. Several of the ten nights I woke up and unzipped to my hammock being covering in ice and my tarp but I was steaming coming out of the bag. This is by far the best sleep system I have ever owned. It lifts very quickly, and is very roomy with plenty of heat to the point of almost being hot some nights. I have never owned a bag where it was snowing outside and I couldn't tell, I just never knew what I was getting up to because it was so comfortable inside. I would give this bad a 10/10 and highly recommend it to anyone who hunts or camps and likes to stay warm. If I had one con to the KSB at all it would be to thicken the footbox, just because it is probably the only place that it maybe was a little chillier, and honestly I was in very bad weather with permafrost in my shelter on a very cold night, but my feet never got cold. I could just tell that it's the thinnest section due to narrow nature of a mummy. It was by far my best upgrade this year. I would highly recommend a good mat inside of it and it will be money for you.