As professional pet sitter Jennifer Roberts explained to us, thickness matters, as well: 'I get grossed out if they’re too thin, then I feel the heat. A good bag is also simple to tie shut, not only to avoid unfortunate leakage but also to prevent getting side-eye from your neighbors as they wonder what’s taking you so long to get that mess off their grass. Opening the bag shouldn’t be frustrating or time-intensive, because nobody needs that stress when they’re about to put poop in their hand. It needs to be easy to separate from other bags, whether that’s on a roll or in a box. The number-one thing a good poop bag needs to do is contain your pup’s business with no leaks or tears.