Access potable water anywhere. This unique and versatile 28MM inline filter threads directly onto popular 28MM opening bottles and flasks and is equally easy to install in any of HydraPak's reservoirs and caps with a Plug-N-Play connect system. This versatile connectivity makes this filter a great backcountry water treatment solution whether you are squeezing your water from a Stow into another bottle, gravity filtering your water out of a Seeker or Pioneer water storage bag or filtering as you drink on the go from a Stow or HydraPak reservoir.