This piece is 10" tall and would fit in a cylinder 8" in diameter.  The Corian base is 4 1/2" in diameter.  The rails are stainless steel and 1/4" chrome steel balls, which are hand fed into the top, are used for the rolling elements.

The balls twirl down the spring, swirl in the first small bowl, then drops to a loop that feeds to another bowl.  Then another.  And another.  Then drops to a track and rolls out to the front.