The Nathan Vaporkrar 2 4L is a fantastic trail running pack. The material feels great, plenty of storage space for being out on your own for 2 to 3 hours at a time and really nice fit. That fit is the strange thing about this pack though. I'm 181cm at 77kg or 5'11 and 170lbs. I'm a European size M or L in most shirts and vests. I wear an M/L sized 12L pack from a major competitor for my long-distance events. I this pack I bought a size S. The sizing is right on the edge. The straps are at the maximum, but I think a size up would make the pack too big.
All the essential bits and pieces are there. The pack comes with soft flasks, an emergency whistle and feels high quality. It's 4 stars, and not 5, for the very high price level of this pack. I got it at 30% off which probably puts it at a much more competitive price range for what you get.