Rehydrate from any fresh water source with the HydraPak UltraFlask+ Filter Cap. This filter fits any hydraflask bottle with a 42mm opening. This filter removes Escherichia coli bacteria Cryptosporidium parvum cysts, and Giardia lamblia from approximately 1,500 liters of water at a rate of >1L per minute. The high-flow bite valve provides fast hydration