The covers are designed for Mona 2.1 speakers (See https://www.acoustic-design-magazin.de/2016/08/19/mona-2-1/ for more information).
The speakers and the covers have a size of 140 x 178 mm.
The mounting holes of the cover is designed for those VISATON frame dowels: https://www.visaton.de/en/products/accessories/cabinet-construction-accessories/frame-dowels
The inner hole can be used for marking the drill holes on the speaker and pushing the dowels out again (if needed).
Make sure to use the thinner 3.5mm side of the strip to secure the fabric in the groove.
Update 31.12.24: Corrected stl file for cover with inner hole.
The author marked this model as their own original creation.