It's a reinforcement for platform of dremel 3D printer E3D20.
This modification improves adhesion of your designs on the platform as it reduces vibration and it solves the Z stepper motor jam problem at the end of the impression, in case you have it.
You can print it by segments or complete with 30% to 40% infill should be enough or you can use more, For best printing results re-tight the allen screws of your printer after installation.
I already tested and it works for me.
you can print it by part or complete in case you have a bigger printer to do it.