I loved this hydration pack initially. I carried it on two 16 mile runs and an 18 mile run. There was absolutely no chafing, although I did have stains on my white shirt as a result of sweating during the run. However, the main problem I had was that it started leaking after my third run where the blue tube connects to the bladder. It really let me down. I don't know if I just got a bad product and I should exchange it or if this problem is inherent. Either way, it is an incredible inconvenience.

This is my first running hydration pack, so I don't have a point of reference, except for a hiking pack from Camelbak. The E-Race is much more stable, and body-hugging. There is still a little bounce when the pack is full, but I don't think this can be avoided in any pack, no matter the design (there is too much inertia in 1.5-2 liters of water). The great thing is that the weight is distributed across the chest as well, and not just on the shoulders. This is a minimalist pack, with just a couple of hip pockets in which to store a cell phone and gu packets. The BOA system does work as advertised, keeping the fluid bladder compressed so it's easy to drink via the bite valve. Overall, I'm very satisfied with this pack.

The bladder has to be taken out of the pack to refill and is very difficult to get back in after it is full. Also, I live in San Diego and run without a shirt a lot in the summer. This pack feels awful if you don't wear a shirt under it. Other then these issues it is a good pack. I plan to return mine to get the Mountain Smith Ultra Lumbar Pack which appears to be much more functional.

Looks cool, very light and compact. Fully loaded with water it stays snug against your back when running. Maybe room for 1 clothing article to be strapped into the drawtie system that holds the bladder. I am xs in womens and it is one-size-fits-all and was slightly long in the torso.

However, not functional for racing due to duration to refill. You have to take pack off and undo the drawtie to get to the bladder. Re put the bladder back and draw tight again.

This will be my second Boa hydration pack, bought so I can swap out mid-marathon this November. Fits great, never a problem with the bladder, can hardly tell it is on. If you have a larger bra-size than me (36C) it may be somewhat awkward, mine always feels a little off for the first mile or so and then things settle down and I forget it is there. Does it look dorky? Yes. Does it do an awesome job of fueling my run? YES.

this pack fits great on your back and is comfortable to run with. bite valve flaps a little but overall a good pack.