Thermos · Insulated Drink Tumblers
Thermos Stainless Steel Tumbler w/ Slide Lock Lid
Lower concern. Stainless steel tumbler with plastic lid of undisclosed chemistry.
The tumbler is stainless steel with no coating on record. The slide lock lid is plastic, but its chemistry is not stated. Thermos has no PFAS statement on record for this product.
We flunk more products than we pass. This one earned its grade. How we grade
Material
Stainless steel tumbler with plastic slide lock lid
Brand disclosure
Brand is silent on PFAS
Lab data
No public lab test
What Thermos Stainless Steel Tumbler w/ Slide is made of, ingredients and materials
The tumbler body is food-grade stainless steel (typically 18/8 or similar austenitic grade), which is chemically inert and does not leach metals into beverages under normal use. The slide lock lid is injection-molded plastic, most commonly polypropylene (PP) or acetal copolymer, neither of which contains BPA in modern formulations. Stainless steel avoids the concerns of aluminum leaching or ceramic glaze contaminants that plague other drinkware; the plastic lid is the only component requiring scrutiny.
What’s concerning
Category baseline
The starting point for this type of product, before anything specific to this product is counted.
No PFAS disclosure
No public statement from the brand about PFAS in this product.
Plastic lid degradation
Polypropylene or acetal lids can develop micro-cracks and surface crazing over 2-4 years with repeated thermal cycling and dishwashing, potentially releasing small plastic particles. Risk is low but cumulative; visual inspection is the primary control.
Bacterial/mold growth in lid mechanism
Slide lock mechanisms trap moisture in crevices that are difficult to clean thoroughly, creating potential microenvironments for microbial growth if lid is stored wet. Regular hand washing and air drying eliminate this risk.
What’s reassuring
Bare uncoated material
Recorded as a bare, uncoated material with no surface coating or treatment.
Stainless steel corrosion or nickel leaching
High-quality food-grade stainless steel (18/8) used in Thermos products is passivated and does not corrode or release nickel under normal beverage contact. No recalls or reports of leaching for this product line.
Coating or finish degradation on lid
Thermos slide lock lids are typically uncoated molded plastic with no enamel, paint, or applied finish, eliminating concerns about lead or cadmium in coatings. The material itself is the final surface.
The full breakdown
The brand's record and disclosure
Thermos (owned by Groupe SEB) has no documented safety recalls specific to this tumbler model and maintains general compliance with FDA and CPSIA standards for food-contact materials. The brand does not publicly disclose material sourcing or chemical testing results, which is typical for housewares manufacturers but limits transparency. No established controversies or safety alerts for this product line have been published by consumer safety organizations.
How it compares in its category
Stainless steel tumblers are among lower concern reusable drinkware options because the material itself is not a material linked to PFAS degradation into beverages. This product is functionally equivalent to competitors like Yeti, RTIC, or Contigo in terms of material safety, though those brands similarly do not disclose chemical testing. The plastic lid is a universal weak point across the category; all slide-lock designs carry minor degradation risk over years of use.
If you buy it
Hand wash the lid regularly and inspect it annually for cracks, cloudiness, or deformation, especially if exposed to heat or dishwasher cycles; replace if compromised. Avoid prolonged contact with very hot liquids (above 150F) in the lid mechanism to slow plastic fatigue. The stainless steel body is durable and effectively non-hazardous; focus maintenance on the lid and keep it dry between uses to prevent microbial growth. An expected lifespan is 3-5 years before lid replacement becomes prudent.
What we don’t know
- Basis
- Model estimate, 78% confidence, not a lab result
- Lab test
- None on record for this exact product
- Brand statement
- Thermos has made none
Formulations change between production runs, so check the current label. How we grade.
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More insulated drink tumblers 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.