I had one on a set of Kintails I bought. It was the large size, and I found it too big to be comfortable. I also had a problem with air efficiency with the pipes, turned out that the bag had partially delaminated, and was leaking through the skin. Not horribly, but enough to have an effect. I don't know how old the bag was, or whether or not that's a common problem with the hybrid bags, just my experience. I replaced it with a Gannaway, and have been well pleased.