Osprey 2L HydraForm Reservoir  (Discontinued Colors)

"I have used this so far only on a few hikes. I can't speak for the longevity. It fits perfectly into my Osprey day pack, and its shape is molded such that it fits along my back. It won't collapse into itself as it gets empty, but it is light despite of the added plastic. It holds enough fluid for a multi-hour hike. The bite valve is easy to operate. It is relatively easy to clean with water and a drop of dish liquid, but it takes a little patience to rinse out and wait for it to dry. In warm weather it dries in 2-3 days by hanging it in the garage, but I have to help by shaking out the collected water daily and soaking it out of creases with a kitchen towel. The extra cost compared to an inexpensive big store bladder is money well spent, and I am glad I did."