Flex · Menstrual Cups
Flex Menstrual Cup
Lower PFAS concern; menstrual cups have no functional need for PFAS, but Flex does not publicly disclose material sourcing or testing.
Flex Menstrual Cup is made from medical-grade silicone, a material with no inherent PFAS use or functional drivers (no water-repellency, stickiness, or grease resistance needed). No public third-party testing or PFAS-specific claims from the brand.
Shop Flex on Amazon →Material
Medical-grade silicone
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
Why this grade
Category baseline
period care is a category where PFAS exposure is more common.
No PFAS disclosure
No public statement about PFAS in this product.
Safe base material
Made from a material with no inherent PFAS use (ceramic, mineral, or natural fiber).
The full breakdown
What it's made of and why it matters
Flex Menstrual Cup is constructed from medical-grade silicone, a thermosetting polymer chosen for menstrual cups because it is nonporous, heat-stable, and biocompatible with vaginal tissue. Medical-grade silicone does not contain plasticizers like phthalates or BPA, which are common contaminants in lower-grade plastics. The material resists degradation during normal use and cleaning at temperatures up to approximately 180 degrees Celsius. Silicone's inert chemistry means there is no functional mechanism for leaching of heavy metals or endocrine-disrupting compounds during the product's intended use.
The brand's record and disclosure
Flex has not published third-party testing results, material sourcing documentation, or explicit certifications (such as ISO 10993 biocompatibility or FDA clearance statements) on its website as of available public records. The brand maintains silence on PFAS testing and does not disclose whether raw silicone suppliers were screened for PFAS contamination in manufacturing. No recalls, lawsuits, or safety incidents related to Flex Menstrual Cup have been documented in public databases. This transparency gap is typical of many menstrual cup brands but leaves consumers without independent verification of material purity.
How it compares in its category
Menstrual cups as a category carry significantly lower chemical hazard profiles than disposable pads or tampons, which can contain rayon, dioxins, and fragrance allergens. Among silicone cups, Flex is not distinguished by certifications or testing that set it apart from competitors like Saalt, Cora, or Lumma. Some competitors voluntarily publish biocompatibility data or carry ISO certifications; Flex's lack of public documentation means it sits in the middle-to-lower transparency tier for the category. The medical-grade silicone material itself is industry-standard and poses minimal established risk if properly manufactured.
If you buy it
Wash with mild soap and warm water after each use and boil for 5-10 minutes once per cycle to sterilize; do not use bleach or scented soaps. Replace the cup every 1-2 years or if you notice any visible cracks, discoloration, or loss of structural integrity. Store in a breathable pouch in a cool, dry place to prevent mold or odor buildup. If you have a known silicone allergy (rare but documented), patch-test or consult a gynecologist before use; otherwise, silicone is among the safest materials for prolonged vaginal contact.
Beyond PFAS: other things we checked
Established hazard classes for this product type, assessed from public information. These never change the PFAS grade; a Likely flag caps the Verdict at “Buy with care.”
Silicone degradation and particle shedding
Medical-grade silicone can degrade if exposed to very high heat, harsh chemicals, or prolonged UV light; microscopic particle shedding is theoretically possible but has not been quantified in peer-reviewed studies of menstrual cups. Normal care (boiling, soap, storage in shade) minimizes this risk substantially.
Microbial contamination (bacterial or fungal growth)
If the cup is not boiled regularly, stored in a damp environment, or dried incompletely, bacteria or yeast can colonize surface irregularities. This is a maintenance failure, not a material defect, and is manageable with proper hygiene protocols.
Heavy metals or contaminants in raw silicone
No recalls or testing data from Flex indicate heavy metal contamination in the finished product. Medical-grade silicone is generally free of lead, cadmium, or mercury if sourced from compliant suppliers, but Flex does not publicly disclose supplier audits or batch testing.
Allergic sensitization to silicone or additives
True IgE-mediated silicone allergy is extremely rare; contact dermatitis from trace additives in lower-grade silicone is possible but not documented in Flex product complaints. Medical-grade silicone formulations typically contain minimal additives that trigger allergic responses.
Coating or surface leachables from manufacturing
Flex does not disclose whether anti-stick or release agents are applied during molding. If present in residual amounts, these could theoretically leach; no independent analysis of finished Flex cups has been published to confirm or rule this out.
What we don’t know
This grade is a model-based estimate from public materials, coatings, and brand disclosure at 75% confidence. It is not a lab result.
No independent PFAS lab test is on record for this exact product. A lab test could move the score in either direction.
The brand has not made a specific, verifiable PFAS-free statement, so part of this score reflects that missing disclosure rather than a confirmed material.
Formulations and coatings change between production runs. Always check the current label before buying.
Safer alternatives in Menstrual Cups
Aisle
DIVA Cup Model 2
Medical-grade silicone (body); no Teflon-type coating or Teflon-family coating coatings
Lower-concern menstrual cup; silicone construction and PFAS-free commitment make it a reasonable choice.
✓Verified PFAS-free by a third party
Ruby Cup
Steriliser
Stainless steel heating chamber with silicone/plastic components
Lower-concern menstrual cup sterilizer; stainless core typical for appliances, but silicone/plastic parts unspecified, contact brand for material detail.
⚠Risky category by default
Ruby Cup
Steriliser Purple
stainless steel steriliser/heating element
Lower PFAS concern; no high-risk coatings typical of this product category.
⚠Risky category by default
More menstrual cups grades
How we score: every product runs through the same public 0–100 rubric based on materials, coatings, brand disclosure, lab findings, and recalls. See the full methodology → Spotted a mistake? Report an error.