The Nissan Stainless Steel Commuter Bottle (a/k/a "Backpack Bottle" of "Flip Lid Thermos") is simply the finest leakproof heat/cold retaining thermos we are aware of. We typically fill one with hot water, snap it shut, and toss it over the counter to our inquiring customer, hoping that it falls to the floor, just to prove the point. It will leak if overfilled. My twin sister in Vermont uses one and complains that she has to leave the lid open while driving or the coffee never cools down enough to drink. This is one thermos where you will not easily lose the lid - the lid stays screwed on top the thermos body; merely unlatch the stainless keeper clip, depress the lid lock button, and the lid will snap to the up position. The thermos is dishwasher safe. We recommend disassembling the silicone lid liner for thorough cleaning and removal of accumulated oils (bitterness in the cup). Available in 12 or 16oz.