As one reviewer noted, most bags will be larger than the wheelbase platform by an inch or so. But this didn’t pose a problem — the bag was plenty stable and our dog was a very happy camper.
Cheapskate that I am, I considered all sorts of dollies before purchasing this one. But this won because: 1) bag stays flat, not tilted — easier on your pet and your wrist; 2) it’s got 5 wheels; 3) it folds pretty flat, 4) it’s light; 5) the handle is the perfect height.
Bonus use: we used the wheelbase to haul groceries to our Airbnb ;) Highly recommend!