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I don't think that part of the tire is open to the outside -- you're seeing a cross-section in the pictures and video.

For airless tires I've used a 4x4 (quad), the tires are open on the side just like these images.

For a passenger vehicle application, these tweels will have sidewalls. You don't hit highway speeds on your quad and that makes all the difference.

In fact you can see that the photo of the EV on their site has sidewalls.