I have not one, but two of the duck down bags. I have been planning to review them for awhile. Before continuing, I paid a big $30 for one and $20 for the other, discontinued.I originally bought one as a liner for weather just a tad chillier than my old two season bag would permit. I bought the second before trying the first.
First, I was astounded by the quality of the sewing on the bags. They are now sewn through, but box construction. The zipper seems of good quality and the design if not cutting edge, adequate.
But...and I should spell it BUT...the fill is grossly inadequate for anything perhaps but the warmest of summer. There are major areas in which there is no down whatsoever. Put you head inside and there is not even enough down to redistribute.
The fit around my shoulders is quite tight.
So, if you can find one cheaply, you are not wide through the shoulders and do not care about warmth, maybe it is a go. It might still work as a liner. I carried both of them this fall for a mid-fall excursion where the weather was supposed to be on the mild side of seasonable, and well, I did not freeze to death. (High praise that!)I put one inside the other and when I found the shoulder area too constricting turned the liner upside down and tucked my down sweater around my shoulders. I was adequately warm in a ultralight tent, despite not having had warm food.
You pay your money and take your chances.