Membrane Solutions S1 Personal Water Filter Straw

What it removes from water, and how well that is proved. 6: A bit better than average.

0.1 µm hollow-fibre membrane. The brand claims 99.99999% of bacteria and 99.999% of parasites (Giardia, Cryptosporidium). Its published SGS report (2 June 2021) tested only total coliforms (E. coli) and turbidity, to Chinese national methods, and no protozoa test is published. The NSF/ANSI 42, 372 and 401 listings are not microbial standards. Bacteria and protozoa claimed with only a partial published test and no named microbial standard, so 3. No virus claim.

How fast clean water comes through when it is new. Real flow drops as it clogs: see Ease of use. 2: A weak point.

0.5 L/min: the brand's own page gives 500 mL a minute, and Ultralight Outdoor Gear lists the same. David On Earth timed its straws at 500 mL a minute, and the NSF listing's flow converts to 0.49 L/min. Under 0.6 L/min, so 1.

How much it adds to your pack. 10: The best you can buy for this.

About 57 g, converted from the brand's rounded figure on its own page. Ultralight Outdoor Gear lists 61 g. Under 90 g either way, so 5.

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.

The Good Ride (3-day backpacking trip) found it very easy to use (4). Oak and Cedar Homestead found it fairly easy to draw water through, easier than other straws it had used; the straw in its video looks the same as the brand's S1 photo (4). David On Earth, who tested this 5-stage straw and the older 4-stage one together, found they clogged after about 7 L of clear water and 2 L of murky water, the same as other popular filters, and needed about a litre of water to backwash (3). Average 3.7 out of 5, so 7 out of 10. All three were sent the straws by the brand or by SimPure, and say so.