They are a soft velour, and oval in shape. They are about perfect for my ears and don't press on the edges of my ears too much. Despite being slightly oval, they have no problems fitting on my Beyerdynamic 880 or AKG K240 Sextett.
As far as sound goes, they did not do well on my beyerdynamic 880. There was too much congestion, and the airiness and treble was gone. The bass and midrange was muffled. I even tried removing the stock beyerdynamic foam driver cover in addition to the foam backing on the pads. The sound was still muffled.
I permanently removed the foam backing built into the pads, and installed them on my Sextetts. Wow! These are the pads I've been searching for. These help bring out the midrange and treble and it's extremely transparent and neutral. Bass notes and percussion hit hard and deep, but with no bloat. It's hard to believe this is a headphone from 1975, because it destroys many modern headphones with this configuration. Highly recommended for vintage AKG, and perhaps even modern pairs as well. I'll test those next.