90xx skimmer design question?

[patchesj]

I'm curious, it appears that the only difference between the 9011 and 9016 is the skimmer cup size. I can understand that the taller 9016 cup allows you to run more air, and thus has a higher capacity rating.

The 9020.040 is the part that I don't necessarily understand. This also raises the capacity rating of the skimmer? It appears to be the same overall height as the cup for the 9011?

 

[rvitko]

It is taller than the 0220.140 (skimmer cup of the 9011), it is actually just an 1" shorter that the 9016 cup but we are only concerned with height of the riser for the performance, not the overall cup height, the 9020.140 has no cup so it is just a riser and a drain and is shorter as a result.