In case you were wondering what's behind the fabric in the official case.
It's not much, but I learned that the case is made with a dual injection mold technique to combine a rubber-like plastic with a hard shell. Essentially, what you feel on the outside is the rubber coating, but behind the fabric and on the side rails inside, there’s a hard plastic (probably polycarbonate, as it dissolves in acetone). The reason I did this was to add a magnetic ring inside the case to make it MagSafe compatible. I’ll probably mill a circle on the inside of the case to set the ring in. Eventually, I plan to cover the inside again.