Is that legal to 'make' a fly wheel?

I’ve seen a lot robots in asia-pasific vex competition using a “self-made” fly wheels. It’s two pieces round cut from a plastic board with a geer or something else in between. Is that legal?
Because in this way, we can acturally use the size we want and together with the gear ratio perfectly matching with it.

Well… if it is using the legal material, e.g. polycarbonate sheet and within the size of 12" x 24", then i dont see why not.
Unless there is something else (illegal) that they used that I am not aware of.
Think it is a wheel legs that is in between the 2 plastic thing.

It is almost like 323 doing their own turntable using polycarbonate. Nothing wrong with that.