This may be useful to owners of AKG 240 MKII head phones. My headphones started to overextend (rotation) and finally, after lending them to my son, they just died. Turns out this little plastic thing inside had broken, letting the ear pads rotate freely, which in turn ripped the cables.
This is a little replacement plastic disk that I used to replace whatever plastic was there before. The phones feel like brand new. This is how to repair:
Use a tiny screwdriver or similar to lift off the cover plate (simply put the screw driver in the little opening and lift). The cover plate is the shiny round sticker thing in the middle of the ear pad with the AKG mark.
Unscrew the screw(s) (1 if R, 2 if L) and open it up.
Fix any soldering problems and unscrew and remove any plastic fragments left from the disintegrated part.
For the right side (only), screw the tiny screw into the tiny hole of the new plastic part to tap it, then remove the screw again.
Push the beams in place (use pliers if necessary (carefully) to click them into place), and put the stretchy band underneath the assembly.
Push the assembly into place (keep stretching the band), screw it down and let go of the stretch band.
Screw on the lid and put the cover plate back in place.
Done! Your headphones should feel like they are factory new again. :)