Review on Stanley Classic Vacuum Insulated Wide Mouth Bottle: BPA-Free Stainless Steel Thermos for Hot & Cold Drinks - 1 QT (32 oz) & 20 oz Options! by Omar Obong

I don't think this thermos has a vacuum seal. I have an old Stanley thermos. . . 15 years old might be a large size. The old one keeps liquids hot for almost 9 hours. The new one is almost 4 hours old and a bit warm. ** I always put boiled water in a thermos for 20 minutes first to preheat it. That doesn't help either with this thermos flask. I can't imagine the coffee wouldn't have stayed warm for even 3 hours if I hadn't warmed it up. I don't know if it's defective (vacuum seal accidentally missing) or made on purpose so it doesn't last 3 hours. I've had 3 Stanley thermoses in the Air Force since 1982. I've been using it for over 20 years and the old one worked great. The last good one for 15 years also worked great. This one has been new for 2 months - never worked well. Hope you were better.