Vertex Zeovit Reator Cleaning - Part Question

[LittleMaui]

While cleaning my reactor, the small part on the left fell out of the pipe. Can someone tell me which way it goes back in? Should the round end go in first, or the flat end?

 

[Reefing Madness]

 

[Ariton]

That part is when the pump stop working the media still to stay wet so the rounded part needs to be on the side where the flow comes from, if you didn't understand me feel free to pm me.

 

[LittleMaui]

I see. Thanks