MakeAnything@Parasol It might be possible to squeeze some ball bearings in this version, but it wasn't really designed for that.. that would require a two part model. I can upload mine but I think the price will be quite high if I make it large enough to hold standard marbles.
Thanks for your order! The effect works best through a camera, but it's still totally convincing with both eyes open.. most important is viewing it from the correct angle. I think you'll be shocked how well it works when you're holding it in your own hands :)