Apple Vision Pro?

So, I was just scrolling through eBay earlier and stumbled onto something that would be an absolute steal if it’s actually what I think it is.
It's one of those Apple Vision Pro things—or at least looks like it—and from what I can gather, you can basically watch movies on them. But here's the kicker: I'm totally lost on how the video actually gets into the headset. Like, does it pull from a USB drive, plug into your iPhone, or maybe run off an SD card?
Check out this link virtual video glasses
Does anyone here actually know how these things work?

It actually says it right there on the images if you scroll down enough.

http://img.auctiva.com/imgdata/1/5/3...33129097_o.jpg

Built in 2 GB, expandable up to 32 GB

though—if you look at the lower specs—it mentions built-in 4GB
Memory Card Slot: Micro SD card slot

so, I guess based on the image (that top left section):
http://img.auctiva.com/imgdata/1/5/3...26656234_o.jpg

you should be able to just plug it into a computer—fill up the internal storage or an SD card, maybe.

So, you're saying the video plays straight from an SD card (4 GB).
I see they've got a bunch of different screen sizes available, like 50", 60", 72", and so on.
The only thing I don't get is what's actually going to change for me if I'm wearing the glasses—is there really a noticeable difference between a 50" and a 72" view?

Since we're talking about "virtual" inches, I guess they probably achieve that effect by adjusting how close or far the screen sits within the headset frame—depending on how many virtual inches you need to see.

I'm looking at picking up some new glasses, but I’m totally stuck between the 50-inch and the 80-inch options.
Logically, you'd think the 80-inch ones would be the way to go, right? But I'd love for someone to break down what the actual difference is between the 50" and the 80" models.