The ball is quite steady in middle of the flow, actually. No boucing around. Those ball + spring valves are quite common in oil pumps, medical systems, and hazardous chemical processing systems. I've seen a lot of em made out of plastic. The ball is made of rubber and provides a good seal against backflow. They come with or withoug spring, that depends on the desired response time.
Without spring the ball 'sticks' to the other side which has openings all around to enable flow (when it's in the good direction)
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