User Review: Mountain Hardwear 3D Upgrade Liner
Design: semi mummy
Temperature Rating: 45
Weight: 1 lb 10 oz
Price Paid: don't remember exactly ~$100
This bag is an excellent choice for hardcore outdoor people. I've used mine on Rainer, in snow, in freezing temps where the water has frozen overnight. Put all your clothes on that you are carrying anyway and climb in for a toasty night (just make sure you put dry socks on).
I just wish I would have carried up Mount Sir Donald for my unplanned bivy there....brrrrrrrrr. Lighten up your pack and go further, higher, and faster.
The only time I use a heavier bag is when I'm car camping in below freezing temps. Too bad they don't make these anymore (people are so stupid).