Great when working properly
Reliability has been questionable. I have used this cool gadget on two weekend backcountry trips. When it works properly it is an amazing product, however sometimes, and more often than not on my last trip, the unit would not engage properly. The light would flash on and then "frown" from LCD would appear, and yes the batteries are new a yes the water was making complete contact with the sensors. I cannnot explain why this happened, very frustrating, It may be an air bubble issue over the contacts when inserted into the Nalgene bottle. Just be mindful of this situation. Overall a cool gadget but if I was alone in the woods with only this as my lone water filter for over a couple of days I might be concerned.