The Platypus Big Zip LP (low profile) Reservoir is a burly hydration bladder that is easy to clean and relatively light. Even though it scores low, it works as a decent hydration system. It didn't have nifty adaptations like other bladders tested, and the quality isn't as high as others. The zip-top closure is intuitive and fast to use, while the quick release system is somewhat compatible with other bladders (and you can change out the mouthpiece).
The slim profile is compatible with many packs, but not all. This opening is a little different than a flip-top opening, as it seals at the top similar to a ziplock bag instead of flipping over itself. We like this design but wish for a larger opening for a few reasons. Also, in cold weather, the top is harder to peel apart to refill. If you're interested in a flip top model instead, check out our Editors' Choice winner, the Geigerrig Hydration Engine. Or if you prefer a screw top option, read up on our Best Buy winner, the CamelBak Crux Reservoir.