I have the Big Agnes Zirkel and the Lost Dog. The Lost Dog is a 50+ rated bag that I use alone in summer and it slides over the Zirkel in winter to allow me to go to lower temps. I will never need another bag. Hands down the best bag I have ever owned and will buy another when this one breaks. No problems here. Just sweet dreams and ultimate comfort. I have the Uninsulated bag...they were just coming out w/ the Insulated when i got mine. I need to upgrade.