The honest context on Knix
Knix settled a class action for $1.4 million (Spencer v. Knix) covering 2020 to 2022 purchases, and as part of it agreed to stop calling products "PFAS-free," "toxic-chemical-free," or "fluorine-free" unless it can support the claim, plus two years of increased PFAS testing. No wrongdoing was admitted. Thinx settled a larger, similar case. If safety drives your switch, judge every brand - including the one you switch TO - by its current published testing, not its marketing words. Our PFAS guide walks through how.
The practical reasons are the usual ones: fit that never settled, a tier that did not hold what you expected (Knix's "Heavy" claims 36 to 63 mL - other brands' "Heavy" can be 20 mL, so a downgrade can surprise you), or price. The picks below carry live prices and verified millilitres so you can see exactly what a switch trades away.
Mind the capacity ceiling when you switch
One thing to know before leaving Knix: by claimed maximums, only Thinx's current styles match or exceed Knix's Ultra (up to about 99 mL, the highest figure any brand states in millilitres). Thinx states "up to 12 regular tampons' worth" and no millilitre figure at all; that works out to about 108 mL on the FDA regular-tampon ceiling. Every other brand we track tops out lower. If you wore Ultra for genuinely heavy days, your realistic alternatives are Thinx at the top of the range, or doubling up with a backup on peak days at any other brand. If you wore Knix's lighter tiers, nearly every brand covers you.
Quick answers
- What is similar to Knix?
- For everyday tiers, WUKA, Saalt, Modibodi, Thinx, and The Period Company all publish verified claims in the same 20 to 60 mL band as Knix's core range. For Knix's Ultra tier specifically (up to about 99 mL claimed), the only comparable ceiling in our catalog is Thinx's current styles at roughly 108 mL, a figure we compute from its 12-regular-tampon claim rather than one Thinx publishes. The ranked list above shows current stock.
- Why did Knix change its PFAS claims?
- As part of its $1.4 million class-action settlement, Knix agreed to stop using "PFAS-free," "toxic-chemical-free," and "fluorine-free" marketing unless it can support those claims, and to increase PFAS testing for two years. It admitted no wrongdoing. So the absence of those words on Knix's site today is a settlement term, not necessarily a change in the product.
- Is anything more absorbent than Knix Ultra?
- In our catalog only Thinx's current styles sit at or above Knix Ultra's roughly 99 mL ceiling, at about 108 mL - and that one is our computation from Thinx's "up to 12 regular tampons' worth," not a figure Thinx publishes. Remember both numbers are saline-lab maximums - the only blood-component study measured far lower real-world capacity for every product tested - so treat them as a comparison scale, not a guarantee.
- Do Knix sizes match other brands?
- No - every brand draws its own chart, and a Knix size is only a starting guess elsewhere. Use your hip measurement in the size finder to get your size at every charted brand at once, including a note on which brands run small or large.
Related guides
PFAS in period underwear: the lawsuits, the testing, and what it actually means
What PFAS "forever chemicals" are, the Thinx and Knix class-action settlements, the independent lab testing, and how to read it honestly - what was established and what was not.
Thinx alternatives: what to buy instead, by the numbers
Every in-stock alternative to Thinx from the brands we track, ranked by verified millilitres - with the honest reasons people look elsewhere and how to compare fairly.
What size period underwear should I get?
Period underwear is sized on your hip measurement, not your usual dress or bra size, and brands disagree, so the same body can be a M at one brand and an L at another. How to get it right the first time.
Want the one-page version of the data behind these guides? The printable absorbency cheat-sheet puts every brand's tiers in millilitres on a single sheet - free, no email needed.
See every alternative with live prices
The full catalog filters by capacity and brand, with weekly-checked prices and stock - or compare Knix head-to-head with any brand we track.