Nothing makes hydration easier than the Platypus Big Zip™ Hydration Bladder. Our premium reservoir comes with an easy-to-clean wide-mouth opening and a low-profile design that fits the back panel of any pack. Use it for your filtration system in camp matched with a GravityWorks Filter Cartridge or throw this in your pack to have clean water on your adventures. They come in 3 sizes for every instnace which are: 1.5 L, 2.0 L & 3.0. Stay hydrated on the trails and keep going!