I need to slim down my sleeping bag quiver - apparently five is too many, and these two see the least use. Both of these bags have been stored either hanging or in large mesh sacks, both have recently been treated with Nikwax Down Proof. No flaws with either one.

Aegismax Mini - 800FP goose down mummy bag, incredibly light and small. Manufacturer says it’s good to around 50 degrees, I believe it, but you should do some Google research for yourself. $55 shipped in a flat rate envelope. 

Outdoor Vitals 15 degree mummy bag - this one is 650FP duck down (I think) and is probably comparable to the Kelty Cosmic 20. I don’t think this one is currently available, but the company has some other stuff on Amazon if you want to read reviews. I have used it around freezing temps and slept well with base layer and maybe a fleece. $70 shipped in the smallest flat rate box I can stuff it into.