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.
one or more gifts or other benefits from the co-op.