This fall I signed up to do the 25K at the Rough Trail Ultra Marathon. It prompted me to look into a hydration pack given the distance. I wanted to carry water but have my hands free in case there is some climbing involved. The race director also told me that each participant is required to carry water despite the water stops given the terrain.
In my Google search, I found the SL3S Hydration Vest/Backpack. I chose a pack because I did not want to clean and maintain a bladder and a tube. (I'm a lazy off trail.) I also did not want to break the bank.
The water bottles are about 300ml each. Each bottle is good for me for about 5 miles. At longer distances I am hoping to be able to refill the bottles.
The chest straps are long so it would suit men and women. I have done 3 long runs with it so far and don't notice the weight. I like the pack since it allows for me to carry all my neurotic stuff like hand sanitizer, inhaler and id.
On the left side is a zippered pocket which was designed to fit an iPhone 6. I keep mine wrapped in plastic. There's also a pocket on the right side that was meant for a key fob. My key and fob are the same so it doesn't fit.
Overall its been a great product. I love the colors, which accidentally matches my Road ID (you can never be too careful ladies) and headphones.
The only downside is that since I wear it on my person, it gets as sweaty as I do.