I am suspecting that the Fleck softener flow control buttons are a single piece of rubber contoured to cause turbulence when the flow goes higher, and thus reduce the flow toward the desired rate. This would be different than the Neoperl aerators which has a rubber ring that expands with flow to reduce the flow.
Here is a sketch of a guess of the cross section for discussion. Roughly right idea? Which way would the flow be, and which side would molded-in numbers be?
Here is a sketch of a guess of the cross section for discussion. Roughly right idea? Which way would the flow be, and which side would molded-in numbers be?