Our flip-top self-closure hamper bags are designed with a flap at the top of the bag which, when inverted closes off the top of the bag to facilitate transport. All of our poly/cotton and nylon styles are made with set-in bottoms which increase the bags' capacity nearly 40%. Sizes shown indicate the open diameter of the bag; bags will fit over round, triangular or folding hamper stands. Some bags come with elastic top to help hold the bag firmly on the stand.