The Costco Packable Down Throws were nice when you could get them, but now, they are very hard to find. They weigh a pound, are supposed to be 700 fill power down and are probably good for 20 degrees additional temperature. My 50 Degree F quilt will go to freezing with one as a liner. If you want to find out more about the throw, the full description is:

Double Black Diamond Packable Down Throw