For some reason, the discourse on Twitter following AEW Grand Slam was that AEW didn't properly factor freight times properly for Brisbane and the company had to get loaned a ring. Well, as it turns out, bad faith grifter accounts usually lie, and this is another case of that.
AEW typically uses a 20x20 ring in the United States, and doesn't ship their rings overseas. There was no instance of forgetting the ring, not planning freight, or anything like that. The plan was to always use an 18x18 ring -- the same size used by TNA, and that was used by ROH, ECW, WCW and virtually every prominent indie company. Most AEW talent came up using an 18x18 ring. It was not 16x16 as claimed online.
WWE traditionally has their own rings that are stored overseas as opposed to having them shipped over. Whether or not the ring used on Grand Slam was the one they'd planned on renting, we don't know, but it was always planned to be an 18x18 ring.
AEW has also used an 18x18 ring in the United States in the past, including for the Britt Baker vs. Thunder Rosa cage match.