My daughter has an older version of the Sub Kilo. It's a nice bag -- Pertex shell, 700 fill. I think it's a little underfilled for its 20-F rating, though. Putting the Sub Kilo and the Ultralite side-by-side showed a significant difference in loft. But she likes it, and it's a good bag for the price. Even better when you can get it on sale.