I wanted a net cup for my Ikea Växer rockwool cylinders, which I'm able to use for several pots. So I designed this one, which finaly is suitable for several round rockwool sizes and different sizes of pot openings.

You're able to customize the inset diameter and height, the wall thickness, the plate diameter, height and thickness. You can also add an additional ring to the plate (clearly visible in the pictures), so it stays in place, if the hole diameter is significant taller then the inset.

And of course, I'm glad about your feedback, suggestions and also, if you have printed your own.

2019-08-01: I've attached a few photos, since I use it now also in planters and there are certainly people who are interested in that too.