I've used this bag for summer mountaineering bivvis…
Fill: 550 fill down
Temperature Rating: 30F/0C
Price Paid: US $100 (sale)
I've used this bag for summer mountaineering bivvis (with a G-tex bivvi sack) both times to around -5C so had to wear my thermals and a thin fleece top to stay warm enough. The bag is made of 1.1oz taffeta, packs down to the size of a small coconut.
Overall a good bag and the lack of a cross block baffle allows you to shift the down from the top to the bottom depending on the situation.
It is a snug fit but the draft collar is not existent. With a warm hat and neck warmer, this bag is great for alpine summit pushes/bivvis.