Is the Hydrapeak Insulated Food Jar Worth It for Hot Lunches?

Here's the mechanism doing the actual work. Between the jar's inner and outer stainless steel walls, Hydrapeak pulls almost all the air out, leaving a vacuum. Heat needs a medium, air or metal, to travel through, so with nothing there to conduct it, warmth or cold can only creep out slowly through the small metal seams where the walls meet. That's why a bowl of pasta can still be steaming hours after you sealed it in. Notice the numbers aren't symmetrical: 10 hours hot, 16 hours cold. Heat wants to escape faster than cold sinks, and the wide mouth that makes this jar easy to eat from and easy to scrub clean is also the biggest exit point for warmth, so the lid does more work keeping things hot than keeping them cold. That same opening is why the 18/8 stainless interior doesn't hang onto onion or curry smells the way plastic does, steel doesn't absorb odor molecules, it just needs a hand wash because a dishwasher's heat and detergent wear down the powder coat over time.