Osprey Duro 1.5 With Flasks is an Ultra-light and Functional Running Backpack Designed for trail Running, Marathons, and long Training Sessions where Hydration and Freedom of Movement are Crucial. With a Volume of 1.5 Liters and two Included soft Flasks, you are Ensured easy Access to Hydration Without Compromising pace or Comfort. The Backpack is Designed as a vest with Adjustable and Elastic Straps, Ensuring a snug fit Without Bouncing or Chafing.