What Water Filters Work with my HydraPak Product? – HydraPak Help Center
42mm Filter Cap | HydraPak
HydraPak 28mm Inline Filter | Cabela's
Amazon.com : BeFree 0.6L Water Filter, Fast Flow, 0.1 Micron EZ Clean Membrane for Endurance Sports, Camping and Backpacking (8019639) : Sports & Outdoors