Our HydraQuiver line of vest packs packs have traditionally been a low profile, no chest pocket, no chest strap type of pack. Well we decided to spin it a bit with our new vest pack which delivers the same comfort, has 2 expandable chest pockets, and attaches via a chest strap. The VP2 vest pack utilizes a 3D spacer mesh with a transparent surface that gives a plush "floating" honeycomb appearance. It's softness makes it comfortable against the skin and breathable, while having minimal stretch. Our traditional shoulder pockets are still on the pack for quick access to your nutrition, phone and other accessory items. This pack is extremely light, extremely breathable, stable under speed yet comfortable for the long haul. 
The way to fit this pack properly is to cinch down the sides nice and snug while leaving the front chest strap loose. This tension is very important as it controls the fit and the front chest strap is for micro adjustments only. 
Sizing Note: Our Double Barrel HydraQuiver may be a better option for ladies if you have a large chest. Sorry to be blunt, just trying to help! If under a 27" chest this pack will likely be too big. Anywhere between 27" and 52" generally fits great. 
Food/accessory pockets on the shoulders and chest for quick access.
24oz BPA Free, bottle based hydration for easy fill, easy clean-up.
Medical grade mesh for maximum breathability.
Weight without bottles: 10oz.
iPhone 6/7/8 in a case will fit into the shoulder pockets, iPhone 6+/7+/8+/X+ will fit in the optional modular bag or in the front chest pockets. 
Storage = 198 cubic inches