They're vacuum bags. I can't say I've found a vacuum bag that is really bad or anything, but I suppose if it didn't fit nicely in the vacuum or something, maybe I'd rate it lower. These fit nicely in the vacuum models that are made to use them.
They could possibly be a little bigger since, without a bag, the vacuum actually has quite a lot more space in which it could store stuff you're sucking up. I don't think I'll count that against the bag, though. The bag makes it nice and easy to clean, though, so it's preferable to use the bag.
Note that if you suck up anything damp in these you'll want to throw them out rather than let them sit in the closet. We cleaned out our dryer and there was a bit of slightly damp lint we sucked up. Stuck the Shop Vac in the closet and a couple months later it was sort of a moldy nightmare. Not a fault of the bags, just an FYI for users. They're unlined paper bags, so on damp materials your mileage may vary.