This looks like a very nice pack - but watch out! The information in this spec. is wrong, the pack comes with a 50 ounce bladder, not 70 ounce. This made a big difference to me as I wanted the larger size. Also, I ordered the "white", which is not white and orange with a bit of gray as it appears in this picture. It is actually orange and gray (where the white is in the picture). Not a big deal, but it was a surprise. Otherwise it seemed ok, but I returned it due to the above...

I bought this to use running and cycling. However, after a few minutes, most of my water is gone. I'm going to try to warranty it--stick with a camelbak or a platypus instead if you need a hydration pack! This will keep you wet but not hydrated!

I couldn't figure out why there was so much discrepancy on the water volume. Half say 70oz, and half say 50oz. The bag will acutally hold 70oz, but you will lose most of that as it drips down your back. There isn't a gasket on the opening.
I bought this for my first 50K ultra. The pack is okay for shorter runs (1/2 marathons) when you don't need to fill the bag. It doesn't have any place to put gels except the back, so you would have to take off the pack. I am donating this one to my kids for our short trail adventures. Bought an Ultimate Direction Wisp and couldn't be happier.

I have used the sailfin for long trail runs for about 6 months. I love it. I respectfully disagree with "Barrett" about its appropriateness for a half marathon. I'm training for a trail half marathon and I love it. I've used it in longer races. Great when you want to blow past the aid station. What's going to slow you down more, the weight of a small plack/plus water (Or Gu20) or actually stopping in a crowd of people to drink. Also carrying a water bottle in your hand or on your waist is way more of an annoyance than a small pack in my opinion. I can keep running and drink, which is the number one reason I carry it. I forget the sailfin is there, unless it's sloshing. (Tip: make sure you squeeze all the air out of the bladder and it won't make as much noise.) On hot days the evaporative cooling effect from the back of the pack (It has some kind of crazy mesh covered neoprene looking back panel material) actually helps keep me cool. Helps stow all my junk when I'm out trail running (light jacket or vest, cell phone, energy gel, etc) which is great if I'm going to be away from my car for 2-3 hours.

I love the freedom of not having to stop for water or plan water into my routes. This 50 ounce bladder holds all the liquid I've ever needed for 10-15 mile runs. The North Face hydration system works better than Camel Back in my opinion as it's easier to get in and out, fill and clean.