The Rambler’s tapered shape is slimmer at the base and wider at the top it fit easily into the cup holders of four cars in our test-everything from a Toyota Prius to a Honda Pilot. That’s because it’s skinny where it needs to be.

It’s hard to find a mug that’s skinny enough to fit in a regular car cup holder but still easy to clean by hand. In our tests we found that things like extra latches, which help make a mug leakproof, also happen to make them a little more annoying to use-after all, it’s a pain to have to press a button or pop a cap up every time you take a sip of coffee. For a lot of users, the Rambler’s design probably hits the sweet spot between easy sipping and a basic level of protection against the worst leaks. Yeti makes clear that the Rambler isn’t leakproof, but we think it could fairly be called leak-resistant. Its simple magnetic opening mechanism allows you to sip easily, then close the latch. That precision fit keeps coffee from splashing, say, if you go over a speed bump while driving, and it slows any leaks if the mug is knocked onto its side, giving you the chance to turn the mug right side up before your coffee leaks all over the floor. The perimeter of the Rambler’s lid is wrapped with a rubber gasket, and the lid sits snugly atop a lip inside the mug. The Rambler isn’t a leakproof mug, but to be fair, it isn’t designed to be. “We found eight other mugs that performed better than the Rambler, including a Zojirushi which kept water hot for 13½ hours, which is about three times as long as the Yeti.” Almost 14 hours is probably overkill for most coffee drinkers, and frankly, the 4½ hours you’ll get from the Rambler might be, too, but it’s also clear that the Rambler is far from the front of the pack. “That might be plenty for most users, and enough to earn a rating of Very Good in our test, but it was far from the best,” Deitrick says. Perhaps the boldest claim Yeti makes for the Rambler is that it has vacuum insulation, “to protect your hot or cold beverages at all costs.” When CR’s test engineer Bernie Deitrick filled the Rambler with water heated to the temperature of freshly brewed coffee, he found that the Rambler kept liquids hot for 4½ hours.

Yeti rambler 20oz tumbler