Flex · Menstrual Cups
Reusable Menstrual Cup | Flex Cup Size 01
Lower PFAS concern; medical-grade silicone has no known PFAS need, but Flex does not publicly address it.
Flex Cup is made from medical-grade silicone, a material class not typically associated with intentional PFAS use. Menstrual cups have no functional reason to include Teflon-family coating or water-repellent coatings.
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
The Flex Cup is constructed from medical-grade silicone, a synthetic polymer selected specifically for internal menstrual use because it resists degradation, does not leach endocrine-active chemicals, and tolerates repeated autoclaving and boiling. Medical-grade silicone (typically platinum-cured or peroxide-cured) is inert once polymerized and has no known affinity for PFAS or traditional plasticizers like BPA or phthalates. The material's stability under body temperature and acidic menstrual fluid conditions is well-documented in clinical literature.
The brand's record and disclosure
Flex provides transparent ingredient labeling and material sourcing on product pages and safety documentation. The company does not publicly address PFAS testing or position, which is notable but not unusual for small menstrual-product makers; no recalls or safety violations are on record for this product. Third-party certifications are absent from publicly available materials, though medical-grade silicone is a regulated material under FDA guidance for intimate-contact devices in some jurisdictions.
How it compares in its category
Menstrual cups (silicone, rubber, or elastomer-based) are generally lower-risk than tampons or pads because they avoid absorbent fiber degradation, synthetic fragrances, and dyes. Silicone cups like Flex occupy the safety mainstream of the category; latex alternatives carry latex-allergy risk; plastic hybrid designs (cup body plus rigid stem) may introduce coating or adhesive unknowns. Flex's material transparency is above-average for the category.
If you buy it
Boil or steam-sterilize between cycles; silicone tolerates high heat well. Replace if the cup becomes sticky, stained beyond cleaning, or shows visible cracks, typically after 5-10 years of use. Avoid prolonged storage in direct sunlight or extreme heat, as silicone can harden over decades. Clean with mild soap and water or fragrance-free cleanser; do not use bleach or harsh solvents.
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 leaching
Medical-grade silicone used in the Flex Cup is chemically stable under body pH and temperature. No published studies document leaching of siloxanes or other degradation products from properly manufactured medical-grade silicone cups during normal use.
Bacterial or fungal colonization
Any reusable menstrual cup can harbor bacteria or fungi if inadequately cleaned or stored damp. This is a user-maintenance issue, not a material defect; proper boiling and air-drying mitigates risk.
Allergic contact dermatitis or sensitization
Rare reports of irritation or allergy to silicone cups exist in medical literature, though incidence is very low. Individuals with known silicone sensitivity should perform a patch test or consult a gynecologist before use.
Dyes or colorant migration
The Flex Cup Size 01 is available in solid colors (typically opaque silicone). No evidence of synthetic dye leaching from medical-grade silicone colorants into menstrual fluid has been published; pigments are typically bonded within the polymer matrix.
Residual volatile organic compounds (VOCs)
Manufacturing off-gassing is minimal with medical-grade silicone if cured properly. Flex does not disclose curing protocols, but medical-grade products are typically post-cured to remove volatile residues before sale.
What we don’t know
This grade is a model-based estimate from public materials, coatings, and brand disclosure at 78% 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.