MSR Hyperflow MicroFilter

What it removes from water, and how well that is proved. 8: Clearly better than most.

0.2 µm hollow-fibre cartridge. MSR says it meets NSF protocol P231 for bacteria (99.9999%) and protozoa (99.9%) from the start to the end of the filter life in worst-case water: a named standard for bacteria and protozoa, so 4. It does not remove viruses (MSR says so).

How fast clean water comes through when it is new. Real flow drops as it clogs: see Ease of use. 10: The best you can buy for this.

MSR gives 3 L/min (about 20 strokes a litre), in the 2.5 L/min and over band. Testers measured less: OutdoorGearLab took 28 seconds a litre in clear water (about 2.1 L/min) and 38 to 48 seconds in its silt test, where it needed backflushing. Banded on MSR's figure.

How much it adds to your pack. 6: A bit better than average.

221 g (MSR), in the 150 to 299 band. Testers weighed the whole kit with its bag at about 300 g (OutdoorGearLab) and 317 g (Mindful Hunter), which would be 2. Ultralight Outdoor Gear lists 244 g.

Filling, squeezing or pumping effort, how fast it clogs in peaty or silty water, and how easy it is to clean. 7: Better than most.

OutdoorGearLab scores ease of filtration 6 out of 10 (3): easy pumping, still energy left after 40 litres, but backflushing is slow and has to be done often. Mindful Hunter (4), an independent hunting channel, likes the pre-filter sheet that works from shallow seeps and says backflushing takes 5 to 15 pumps, with an airlock trap to avoid. Scott Fiddes (4), a short owner video, fills a litre with little effort. Both videos are the owners' own, with no brand link in the video or its description. Average 3.7 out of 5, so 7 out of 10.