This post reviews a Zojirushi Stainless Mug (basically a Zojirushi thermos) that I bought and used for outdoor and traveling with tea.
Preparing for a trip during which I knew I’d be drinking tea mostly outdoors, I decided to take a good thermos. That way, I could fill it with water to drink or hot tea–one vessel would work for either. This was going to be a more rugged trip than my usual traveling style, so I didn’t pack as much teaware as I usually do.
My old thermos leaks, so I wanted something better. I’d heard good things about Zojirushi, so I bought their 16 ounce “stainless mug.” I don’t know why they call it that and not a thermos!
Slim Profile
Let’s start by reviewing this Zojirushi thermos to note that it has a slim profile that’s easy to hold. It is also thin enough to slide into my water bottle pocket of my backpack. It comes in a number of different colors.
Lid
I liked how the lid was designed for drinking. It released a nice, careful flow of liquid through it.
The Zojirushi stainless mug lid was easy for me to screw on. I also appreciate the locking feature so the lid doesn’t accidentally pop open while transporting the thermos. I never had any leaks.
Zojirushi Heat Retention
It is excellent at retaining heat. In fact, I realized I wouldn’t be able to sip tea directly from the thermos even hours after making it because it would still be way too hot! So, I carried a teacup to pour the hot tea into or to steep my tea with the hot water so it could then cool to a safe drinking temperature. I prefer to drink my tea out of a cup anyway. (P.S. I also bought separately and added the “breathe” sticker on the thermos in the nearby photo.)
The other solution would be to let your tea cool to near comfortable drinking temperature before pouring it into the thermos. But, read on for my thoughts on that.
Size
I reviewed Zojirushi thermos sizes. They sell thermoses or “stainless mugs” in bigger sizes, so if you need hot water or tea for more people, you may want to size up from the 16 ounce version.
Prop 65 Warning
When I received this thermos, there was a [California] Prop 65 warning listed on the box. According to the California government’s website, “This law requires businesses to provide warnings before people are exposed to chemicals on the state’s Proposition 65 list.”
I emailed Zojirushi. I wrote:
“[T]he box the thermos arrived in has a Prop 65 warning for cancer and reproductive harm. But, it doesn’t saw [sic] what parts of the bottle or materials necessitated that warning. Can you please provide me this information?”
I definitely wanted to have this information before using or reviewing the Zojirushi thermos!
Support at Zojirushi responded on 3/10/26:
“Thank you for contacting Zojirushi America.
The stainless steel in the interior of the vacuum mug and spring in the lid contains nickel. Nickel is an important alloying element in food-grade stainless steel. It provides high anti-corrosive properties to the stainless steel (surgical steel contains nickel). The sticker on the bottom of the outside of the vacuum mug contains DBP.
Please note that the bottom of the vacuum mug does not come in to direct contact with food or beverage. For further information, please go to www.P65Warnings.ca.gov
Proposition 65 enables Californians to make informed decisions about their exposures to certain chemicals. This product contains chemicals known to the State of California to cause cancer and birth defects or other reproductive harm. For further information, please go to www.P65Warnings.ca.gov
…
Please note that the warning does not mean that our products will necessarily cause harm or that they violate any product-safety standards by the FDA. In fact, the California government has clarified that ‘the fact that a product bears a Proposition 65 warning does not mean by itself that the product is unsafe.'”
Nickel & Stainless Steel
I didn’t even know that food grade stainless steel (18/8-18/10) contains some nickel until researching this issue! If you have a nickel allergy–you probably already know this and might already avoid stainless steel water bottles and thermoses, etc. Otherwise, everyone should research the issue and come to their own decision.
I am guessing most stainless steel thermoses will have this warning. It’s a matter of reading the fine print and following up. As I thought over this issue with the Zojirushi thermos for this review, I’ve decided to keep and use it; however, I’ll probably stick to using it to transport hot water to make tea in a cup or teaware instead of putting acidic tea directly in the thermos.