A very large bag with a reinforced bottom layer.  Is very good for cleaning up the yard as it can hold 2 to 4 messes in a single bag.  I am cleaning up after a 7 month old German Shorthaired Pointer so as to give you a perspective of the capacity of the bags.  Also these bags are packed such that they are stacked one on the other, no need to tear bags apart.  They are easy to separate at the top, no fumbling with thin plastic edges that will not come apart.