Gravity-Fed Water Bag for Sawyer Survival Water Filter Straw, 1.5 Gal Large Gravity Water Bladder Compatible with LifeStraw and Other Water Filter Straw, Foldable, BPA-Free (6L)Connect with Filter straw Compatible with LifeStraw, Membrane, and other common brands Filter Straw Filtration System. Make your filter straw into an outdoor water purifier. The spout is designed on the side to complete the primary sedimentation filtration of mud and sand in the water, preventing mud and sand from entering the filter (filter straw); thereby protecting the filter and extending its use time. Large Capacity: With 1. 5 gallons of large