From Rab:

Built for the intrepid mountain runner, this 6L capacity running vest features two 500ml flasks (included), water bladder compatibility, multiple handy pockets, and a breathable, supportive Mono Mesh Chassis to keep you ventilated on your most challenging runs.

• Volume:6lt / 365cu.in
• Weight:0..32kg / 11oz with flasks 0.24kg / 8oz without flasks (Size M)
• Product Code:QAP-40
• Multi directional Mono Mesh Chassis for enhanced support, reduced bounce and supportive fit
• Stretch side panels provide optimal support and improve fit
• Lightweight fully adjustable and customisable sternum fit system
• Secure YKK® zipped pocket on upper back yolk
• Internal back panel sleeve can hold a 2L hydration bladder
• Upper back and dual access lower stretch stash pockets
• 2 upper flat stretch pockets and 2 lower vest front stretch stash pockets
• 2 500ml soft flask pockets (soft flasks included)
• 2 front YKK® concealed stretch mesh pockets with ultralight zip pulls
• Rear bungee pole holder for on the go storage
• Silicone print on lower hem
• Chest: S:34-37" M:37-40" L:40-44"