This is the Camelbak H.A.W.G which is a medium sized day-sack that has in build reservoir.

Lets break it down, here are the main objectives for this amazing piece of kit - 

• The reservoir holds 100oz of water  - MILSPEC reservoir thats offers 25% more water per  sip. 
• Air director back panel is designed to accommodate another 3L.
• Inside the bag you have two full length compartments to help keep your items organised. 
• Extended MOLLE on the front area of the rucksack to enable you to attach more Molle pouches to suit your needs.
• Top webbing hang loop
• Side release shoulder straps 
• Adjustable Sternham strap
• Removable waist belt
• Upper and Lower compression straps
• Lower drinking tube exit ports to enable under arm routing.
• Capacity 23Litres
• Pack weight 1.2kg
• Dimensions of the day sack - 48CM X 27CM X 26CM