This diverter plate is compatible with Waterway Dyna-Flo and Flo-Pro skimmers. 

You can adjust the water flow through the skimmer by turning the two discs against one another to vary the size of the hole.

In the case of the Flo-Pro skimmers, a plug clips into the middle of the plate, and stays there - it is very hard to remove once in place. 

The plug and plate together are positioned on top of the filter and just under the filter basket.