Guardian Stainless Steel Mug vs Stainless Steel King Travel Mug: which is safer?
Thermos Guardian Stainless Steel Mug is our pick: better on PFAS and on the overall hazard picture.
Our pick
Thermos
Guardian Stainless Steel Mug
PFAS grade
A 95/100
Overall grade
A 91/100
Verdict
Buy
Hazard flags
⚑ 1
Material
Stainless steel (uncoated)
Confidence
85%
PossibleBacterial growth in storage
Thermos
Stainless Steel King Travel Mug
PFAS grade
A 95/100
Overall grade
B 83/100
Verdict
Buy
Hazard flags
⚑ 3
Material
Stainless steel interior and exterior, plastic lid
Confidence
82%
PossiblePlastic lid polymer degradation
PossibleGasket/seal material composition
PossibleThermal shock stress on seals
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 travel mugs: see the full ranking