Overflow prefilters, the round ones inside the O.F.

[witecap4u]

How bad do the round prefilters that go in the overflow cut down the drain flow rate. I would think that it would be quite a bit. Anyone have anything to say about using these.

 

[mal]

I tossed mine. It did nothing but collect goo that I had to clean out. My overflow seems to be more quiet without it as well.