It's called a "wing set".
I was given a Kreepy by a neighbor that was moving out of state.
While it works fine, a few weeks ago one side of the wing-set (which had hardened and deteriorated) broke off. The replacement part is about $24 locally.
I've used the Kreepy since then, and honestly...haven't noticed a difference in any level of performance. I've looked hard at the part and I'm stumped as to what it's function is.
I'm tempted not to replace the part...but I'd still like to know what it's supposed to do.
Here's another picture. The wing-set is (are?) the two large light-blue flaps that sit on top of the pleated round pad.
Any ideas as to it's function? Am I missing something important by not replacing it?