Decent hydration reservoir - CamelBak Omega Water Beast Reservoir 100 Oz 90352 (NSN: 8465015956522)

The hydration reservoir works pretty well. It's a little long, which makes it difficult to fit in some packs, I would prefer if it was a bit shorter and wider. I like the insulated drinking tube, which makes it less likely that the tube will freeze in cold weather. The real feature that this reservoir lacks, which is why I only gave it 4 stars, is that when the drinking tube is disconnected from the bottom, there is no valve that shuts and water just runs out of the bottom of the reservoir. This means that in order to refill it, the drinking tube must be removed from the pack along with the the reservoir. It's kind of a pain in the neck to have to re-thread the drinking tube thru the side of the pack and along the pack straps each time you refill it. Other than than that, it's a pretty good way to carry your water.