Stainless King Tumbler vs Stainless Mug: which is safer?
Stainless King Tumbler is our pick: better on PFAS and on the overall hazard picture.
Our pick
Thermos
Stainless King Tumbler
PFAS grade
A 95/100
Overall grade
A 91/100
Verdict
Buy
Hazard flags
⚑ 1
Material
Stainless steel interior, plastic exterior lid
Confidence
78%
PossiblePlastic lid degradation and leaching
Zojirushi
Stainless Mug
PFAS grade
A 95/100
Overall grade
B 83/100
Verdict
Buy
Hazard flags
⚑ 3
Material
stainless steel, no coating specified
Confidence
82%
PossibleNickel leaching (from stainless steel alloy)
PossibleBacterial growth in trapped water (between walls)
PossibleThermal stress from extreme temperature swings
Both products run through the same public rubric: materials, coatings, brand disclosure, lab findings, and recalls, plus a beyond-PFAS hazard analysis. Grades are model-based estimates, not lab tests. How grades work →
More insulated drinkware tumblers: see the full ranking