The Miller High Life neoprene bottle koozie is made of the same material as wet suits. It has the strange ability to regulate temperatures. A wet suit keeps your body warm when surrounded by cold water.
For a koozie, it keeps the beer cold while keeping your hand warm wrapped around it. That's because it's an insulator. Temperatures stay right where they are because that's the design of the material they are made.
Made of neoprene, the same material of wet suits