I'm not sure what to make of these almost a year after starting to use them, because some of the bags have held up perfectly, rock solid with stuff inside them and the air sucked out... whereas a couple of the largest ones have not maintained their vacuum seal and are functioning just as large storage bags (which isn't totally useless but isn't what I was looking for). It's possible that the bags work best with certain kinds of items inside; for example, I seem to have worse luck in using them with items that are already very air-filled, like a down coat. By contrast, they've been great for more solid fabrics like denim and evening dresses.  

Pros: When it works, it's great
Cons: Can't count on them entirely, and it's hard to estimate size