Ther-Mo-Pack Mason Jar Container
This container by Lockwood Products from Chicago, holds a quart fruit/mason jar and keeps the food therein hot or cold for hours. As the label says, it "converts your empty fruit jar into a vacuum jar".
The seal on the Ther-Mo-Pak is very tight and would tend to lend credence to the claim!
The container is 22cm(8.75") tall and 14cm(5.5") external diameter. It holds a 1 quart mason jar (included).