That is a GREAT question! It is a common misconception in the cooler world that just because your cooler has a zipper on it, the cool will stay in. That isn’t completely true. Most soft coolers are constructed without any insulation behind the zipper so this area of the cooler is the least effective at keeping the contents cold and the heat out. Zippers are also notorious for snagging onto things or catching on the body of the cooler as you try to open it.
Our Zipperless™Coolers are made so that the plastic of both the lid & liner overlap at the seal (think of this like a fridge). Foam insulation covers the entire surface of the lid and extends right up to the top edge of the liner…meaning your contents stay colder longer!