Used it twice now.
First time -5 (celcius) in a goretex bivi. The bivi was wet all over (on the inside) the bag perfect dry (had to ventilate a lot, but it wasn't to hot).
Second time -15 (celcius) no tent or bivi.
Still had to ventilate a bit.

I have the XL wich gives lot of room (you can store boots and clothes in food section).
Closing the zipper completely takes some effort (becorse of the curve and the position your in?).
The finishing is perfect i couldn't find something wrong.
Pakking takes some effort becorse the Dryloft lockes the air in (while sleeping in it this couses the bag to lofts perfect it looks and feels like its pressurised).
Compared to the TNF Solarflare (similare bag, I wanted to but that one but was sold out every where) it is less luxury, lighter, similar price rating.
I ordered it via the internet it arrived three days later. If i could buy it by a local retailer i gues it would be a bit cheaper (shipping costs and tax) but could not find one that sold them.

Similar Products Used:

I can only compare it to a old sythetic bag it is replacing Nomad Falk (-25 celcius, breathing outher material). Compared to it the king tut is lighter (a lot)
warmer (a lot)
has a bigger temp. range (the nomad was to hot at -5 celcius to sleep in (when new and with maximum ventilation))
smaller to pack (a lot)
better breathing

Being in the armed forces, the requirement for extreme cold weather sleeping bags is large. The current down-filled bags only protect to -35...that's with both layers. The King Tut bag offers protection of -55 degrees Celsius, more than enough for your everyday outdoors person, but just enough for my use. However, if the dual bag is what you're looking for, I suggest you also purchase a flannel liner. The liner helps protect the bag from perspiration and is easier to keep clean, rather than having to spend big $ to get the whole mess dry-cleaned.