Update on my HP-2... they appear to be stock. Just a small piece of light foam on the back of the driver (adhered over the years) and a lot of loosely placed felt strips around the circumference. The foam disintegrated when I touched it (left side of pic) and the felt moves around freely. I already played around with replacing the foam but I still have significant volume separation between the L and R driver. Waiting for new pads to see if maybe that could be the issue. TL;DR - just buy these if you find them cheap, holy shit. So comfortable and very easy to play around with.