@Darryl Thanks for reaching out!

We have several good options for hydration day packs that should meet your needs. Here are a few:

• Osprey Skarab 30 Hydration Pack
• REI Co-op Trail Hydro 30L Hydration Pack
• Gregory Citro 30 H2O Hydration Pack

Some of these might be a little big in terms of the pack itself, however, if you're looking to carry 3+ liters of water you will appreciate the structure of the bigger pack. Some of these do come in a smaller version, but it is good to bear in mind that the hydration bladder also gets smaller.

Hope this helps!

Would these daypacks be able to handle 15 - 20 pounds of weight for rucking? If not, would you have other recommendations? 

@Cheryl_M if those packs fit you well, they can accommodate 15-20lbs (depending a little on the bulk of what you're carrying to get to that weight).

For the original member, having a hydration system included was important so all of the packs we suggested include the hydration bladder - is that also important to you? If not, there are other packs you might consider for rucking. Further, the packs we suggested above will be men's/unisex sizing and will have similar options using a women's specific fit:

• Osprey Skimmer 28 - Women's
• REI Co-op Trail Hydro 30L - Women's
• Gregory Juno 30 - Women's

We hope this helps; let us know if you have additional questions!

By "2.5 - 5 liter" do you mean the bladder capacity or the volume of the pack in general?

I've had an Osprey Raptor 10 for about 8 years now. It works well as a mountain-bike pack and a light day-hike pack. I also use it for winter runs when I want to add or shed layers of warmth. It rides close to the body without a lot of bounce, so I like it for that. It came with a 3 liter reservoir for hydration, which I always assumed was part of the 10 liter total (?). My wife has a larger version of the same pack.

I have soaked the thing in sweat and dust many times and rinsed it clean. It has held up well under my abuse.