Filter water on the go. The new 42MM Filter Cap threads seamlessly onto all sizes of HydraPak&';s 42MM threaded Seeker water storage bags and Flux flexible bottles morphing them into filtration solutions. The end result being lightweight filtration kits that can either be used to squeeze filtered potable water into other camp bottles and containers or to drink freshly filtered water from a Seeker, Flux, UltraFlask or SkyFlask. Both deliver fast and easy water treatment around camp or on the go. Weight 57 G / 2.0 oz Dimensions 42 mm Material PP/POM, EPDM, Silicone, Hollow Fiber Care Avoid freezing filter. Freezing may ruin the hollow fiber membrane. If in freezing conditions we recommend you keep the filter in your pocket or near your body to prevent freezing.