Non-slip scratch resistant rubber base
Customer Reviews:
Stainless steal cup 
My husband loves his cup. I’ve had no complaints from him. The very nice thing about this cup is that it has a stainless steal interior which is very important when pouring hot liquids into it. If you pour hot liquids into a plastic lined cup, the plastic releases toxins into your beverage. Plastic is made of petroleum products.
Some great qualities, but it’s bad qualities are very, very bad! 
Thermos generally makes excellent quality, durable products. This mug keeps hot liquids very hot and cold liquids very cold, for a long time. Also, the tab over the drinking hole is detachable so you can clean out the sludge buildup. Most importantly, it has a stainless steel interior. Plastic interiors retain flavors and make drinks taste terrible. Unfortunately, the lid just slides off an on, really easily. So when this wobbly mug tips over, the lid comes out and the coffee follows. If you lie the mug on its side, tie a thread to the lid, and tie the other end of the thread to a centipede, the centipede will have no problem pulling it off. I tested this. After pulling the lid off with ease, the centipede yawned sarcastically. This type of lid is much less costly for them to manufacture. I would have paid a few bucks more for a screw-on lid. Don’t waste your money.
What a disaster of a cup! 
How can this be loved? Yes it does keep stuff HOT! I wanted a mug that did that and I had seen this at Brookstone during Christmas shopping, but after, they were out of stock, they referred me to Target for the same exact ones..so I bought it there for about 15 bucks.. First off…What gives with the slide on lid with a rubber skim seal???? This thing pops off at its own when it wants to, so be careful! Second, if you even remotely get close to tipping this while full (like getting into your auto), the lid will pop off!! … and if it was a minor bump, the lid will leak thru the removable (to clean) slider/closer. So, its very awkward in how it must be handled. An email to Thermos regarding the quality of this has gone unanswered. I love the mug, the color, style the feel in my hands, fits the cupholder great, but these short-comings are just too much to enjoy it. I will seek out a discontinued Starbucks Curve Mug (which my wife has). That thing is a tank! It also keeps things HOT, rubber grip, spill-proof lid and SCREW ON lid… Thermos…If you add the screw on no leak lid, you have a winner. I will pay good money for a mug that performs, so I will continue on my search.. Hope this helps..
Keeps it COLD, too!! 
My husband & I love this cup. I like hot drinks, and this is great for that, keeps drinks HOTHOTHOT–BUT! My man, he loves the icey cold berverages…this one will keep ice FROZEN in the cup all day long with minimal melting, no joke! I am buying a second one because we fight over the one we rec’d as a gift…it’s worth every penny, too!
Double-walled, vacuum, Thermos brand cup - easly to dissasemble and clean too. 
Yep, these things are great. They are really a double-walled vacuum insulated cup. They are not those cheap plastic or single walled metal cups you get as company promo/schlock. These will keep your coffee hot for a really long time - an hour easily. Warm enough to enjoy for a couple of hours.
The lid comes apart for easy cleaning, there’s no hidden cavity under the slider for coffee/cream/milk sludge to build up. The lid snaps apart and back together easily so you can get the lid clean inside and out and in-between. (Once you buy one, you have to take your old coffee cup’s lid apart and look at all the slime you’ve been sucking on every time you drank coffee!)
The only thing Thermos needs to work on is having a larger air hole so when you are drinking your coffee it actually flows out of the cup. The air hole is small and when coffee splashes up against it, it can make getting coffee out of the drinking hole difficult. Pushing the slide cover more towards the center position usually gets enough air flowing that you can drink that steamy hot coffee.