Nice looking bag, but feels a little overengineered. Almost feels more complicated than it needs to be with the number of compartments and pockets inside. The "hidden" water bottle gap was hard to work with. I was hoping the black webbing would have some elasticity, but it doesn't so shoving a water bottle into that slot isn't the quick seamless action I was hoping it would be, unless you have a skinny bottle that has the form-factor of small umbrella... speaking of which... that slot is probably better used for an umbrella than a water bottle. When the bag is filled out, it doesn't feel as comfortable to wear. Anyway... I think there's a nucleus of a good idea here, but still needs a bit of work and some tweaks. As far was what size water bottle I was able to shove in, I was able to slot in a 16 oz Zojirushi travel mug, but it does feel bulky.