Just Amazing. I own a Stanley Classic Vacuum Bottle and have owned other's like in my life. I thought since there was a large snap on plastic lid on the FRZN vacuum tumbler, it wouldn't work nearly as well as the classic vacuum flask. Well, I was completely surprised and amazed how well it works with just a plastic snap on lid. And it snaps on tightly, too.My wife and I went to a doctor's office and we were running late, so she heated up her cup of coffee a little more in the microwave oven to offset heating the inner wall of this tumbler. But it certainly wasn't boiling hot. About 45 minutes later we arrived and she took a sip through the small hole and burned her lip and her mouth. So she just left it in the car we parked in a multilevel parking garage. The temperature was in the fifties and the car was shaded by the parking garage. An hour and a half later we came back to the car and she burned her lips again. This was 2¼ hours later.We stopped to get groceries on the way home and after we finished, it was still uncomfortably hot. She does like her coffee hot. So I decided to try it. It burned my lips and tip of my tongue and I didn't try it again. After we got home, she was finally able to drink the coffee - a total of 3½ hours after she poured into the tumbler. I wish I had measured the starting temperature, but I didn't.Last night, I put some well frozen ice cream into it and left space for my favorite cold A&W Root Beer to make sort of a root beer float. I thought the ice cream would melt into the surrounding root beer while watching a two hour movie. The tumbler is tall, so the straw wasn't quite touching the bottom. When I got downstairs, I noticed a fair amount of the ice cream was still mostly frozen. So I put it into the refrigerator overnight. It was still in about the same state the next morning. So I gladly finished it off as a pre-breakfast dessert.So whether you want to keep it hot or cold, this is a very remarkable device. I could have gotten this free on the Amazon Vine program, but since it wasn't very expensive, I decided to buy it instead. Now I wish I had gotten the free one and bought a new one at the same time, because I've got to buy another one for myself. My wife has taken possession of this one for her coffee. It's easy to clean. I put in a little dishwashing soap and brushed the sides and bottom and rinsed it out. Cleans up very easily.