@shouston1 thanks for the question! Two things to consider:

  • How big of a hydration reservoir can fit - although the pocket in the back of the Flash 22 can technically fit up to a 3L reservoir, we would recommend one that is 2L or smaller so the reservoir doesn't sit on the bottom of the pack when filled and also doesn't take up so much space in the pack you can't fit anything else!
  • How the reservoir attaches at the top of the pack - the hook in the Flash 22 is actually very versatile with the Velcro loop, so it can accommodate pretty much any style reservoir.

Here are 2 specific reservoirs that we found to fill really well in the Flash 22: Hydrapak Shape-Shift and the Osprey Hydraulics.

For more information on hydration, check out our Expert Advice series! Hope all of this is helpful!

At REI, we believe time outside is fundamental to a life well lived.