For sheer pumpability, the SweetWater is our favorite filter. It moves the wet stuff smoothly, with heaps of mechanical advantage. A clever adapter fits the 11-ounce filter directly to Nalgene and Platypus bottles and bladders. The SweetWater pump is not strictly a purifier, but it stakes a claim in that direction because it's packaged with a bottle of chlorine dioxide drops, hence "system."
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