Steripen Pre-Filter

Sized to fit on Nalgene and other wide mouth bottles, the SteriPEN prefilter prevents particulates over 4 microns in size from entering the bottle. Useful when clear water is not readily available, the filter simply screws onto your bottle, which is then filled with the available water. Remove the center cartridge; place the Classic into the opening, turn upside down and dose the water as usual. If you use the Adventurer-just remove the filter entirely and dose the water as you would normally.