The platypus big zip lp hydration pack has an improved 30 slimmer low profile design to fit better in your pack but has kept all its great platypus features to make it incredibly reliable and user friendly ideal for hydration on the go the big zip offers the fastest drip free flow thanks to its hyperflow bite valve and clean bpa free tasting water on the go it also has a slimeguard antimicrobial treatment to keep your reservoir fresh the wide mouth opening and slidelock closure system make clean