As a father of 1 year old, I see that the hole in my sonos sub is very interesting for my child, so I wanted to find some kind of protection for membrane. Found one on thingiverse created by Bak81, and decided to split it in half to be able to print it in my A1 mini. It came out really well. It has a snug fit, but I am sure, my kid won't tear it out.