Remarkably keeps things cool or hot BUT…..
So overall the product is well designed, I guess, works well. Lid is an excellent device. Well crafted. Unfortunately after short term use it has developed a sort of “rattle” in between the layers. Sounds like loose metal or glass. I never dropped the mug so it must be a design flaw. Always washed by hand also. It’s rather annoying to listen to it’s noise every time you sip out of it. Makes me wonder if it’s safe to drink out of now.