Very good warm weather bag that does what you need it to. Its lighter and packs down smaller than almost any other bag in its price range, which is why I bought it. The long version fits me very well even though I'm 6'3. With my thermolite liner I've slept well in temps in the upper 20s. The only drawback in my opinion is that the zipper doesn't go down quite far enough.
"UltraLamina 45F lives up to it's billing. Great light-weight summer bag that can handle the chill."
I used this in cool conditions, somewhere in the 45 degree range. It was comfortable and warm. I did, however, use a silk liner which may have given me 5-10 degree more protection. What I love about it is how tiny it packs with it's included compression sack. Packed for a week for a trip to Honduras mountains and couldn't afford more weight or volume. I would prefer a little longer zipper on one side. Other than that, I couldn't be more pleased. While in mountains of Honduras and what must have been the rainy season, this bag performed flawlessly. I'm packing again for my upcoming trip and that little bag will be with me.