Let'er rip... Well the zipper did rip. Was shipped a replacement quickly. Stil a happy customer. I have not had a chance to test this in very cold weather yet. I wish these review reminders would wait about 6-12 months for a more acurate review. Other wise the bag look well made and included a longterm storage bac (large) and a backpacking sized one also.
Maybe more later

I use this bag for winter mountaineering and mid winter ski trips where I will be sleeping in a tent. I LOVE it.

The bag has a COMFORT rating of -20f (-29c). Some reviews out there have mentioned the extreme rating (more of a survivability rating) at -40c.

The 800 fill down is excellent and very light, and the 15 denier by 15 denier ballistic ripstop DWR treated nylon is lightweight and surprisingly strong. It will bead water like the best DWR treatments- if you spill a water bottle on it, the water will roll off. However, long term condensation or prolonged exposure to standing liquid can cause the nylon to absorb some water.

The most unique feature of the bag is the stretch design. This does two things.
1- it allows the user to comfortably move inside the bag. Because there is extra room, one can wear extra layers without having to worry about the "push out" effect that can cause most conventional mummy bags to compress their down and cause the bag to not be as warm.

2- The stretch design conforms the bag to the user's body, eliminating dead air space and keeping the user warmer. With less air space to heat up, your body doesn't have to metabolize as much energy to keep you warm.

This bag is surely one of the best on the market. The only change I would suggest is an option for a dryloft bag with a membrane water proofing for additional protection in moist environments.

Note the sizing differs from most companies- the regular is only a 5'10'' bag and the long is only a 6'4 inch bag. I'm 5'11'' and find the long perfect in that I can fit my boots and cloths I want to keep warm in the bottom of the bag with me.

Also note that opposing zipper Montbell Bags can zip into each other- (left into right) for all bags both synthetic and down and regardless of length. My girlfriend and I zip a MB UL SS #2 into this bag and orient the bags put the EXP on top (instead of side by side) for winter couple camping.

One last thing- besides the added room for storage, the long is a great option for shorter people because foot box area of the bag can fold in on itself and cinch down inside the bag, allowing for either a down pillow for your feet or an extra super thick layer of down on top of your feet to keep you extra warm. To do this, just push the footbox into the bag and pull the draw string about 6 inches from the bottom of the bag.