Aquamaxx reactor. What is this screw

[Tangdora]

Hi all.

Definitely putting too much thought into this. But picked up a few aqua max reactors today. Any one have an idea. What this random white screw on the perforated disk is for.

 

[Mr. Mojo Rising]

IDK. I looked at mine and I don't have that screw, mine is about 4 years old though. But still, I can't think of what it's purpose could be...

 

[Gman83]

It is to grip/ grab that plate if you pull out the center