@achadwick@bikes@mastobikes@cycling I get about 10-15 degrees C of protection (translating from F, where my dry-bare-hands limit is 45F, but bare hands in bar mitts gets me to 20-25F). The first few minutes of bare fingers on cold grips takes a little getting used to.
I have upright bars, and once or twice when I needed to brake quickly with a hand out, I just grabbed the entire mitt and squeezed, you might want to try that once or twice before you need to do it in a hurry.