I’ve owned my REI Sub Kilo 20 down sleeping bag for about 2 years. It’s a pretty utilitarian mummy sleeping bag that provides good value at a good price ($239). Like all down bags, it compresses down very well and takes up little room in your pack. It is also fairly lightweight weighing 28.7 oz. The Sub Kilo 20 contains 750 goose down fill and has a comfortable polyester tafetta lining. The outer shell is ripstop nylon. The bag also has a full length zipper, but I’ve found that this snags fairly easily and you need to be careful with it.
However, in my experience the Kilo’s temperature rating is over-rated. This is not a 20 degree bag. Personally, I think that rating is probably closer to 30 degrees provided you have a thick sleeping pad underneath you. I have spent many a cold night in this bag and would not recommend it to someone who is looking to make an investment for serious 3-season backpacking use. It is fine for use in high summer but if you plan on camping in early spring or late fall, get yourself a better bag. I’d recommend checking out a Western Mountaineering Ultralite 20 bag which has 850 fill goose down and is amazingly warm. It’s a bit more expensive, but I expect mine to last for many years to come.
Disclosure: The author owns this product and purchased it using their own funds.