I don't know, I actually bought those velour pads for my JVC S500 headphone to try to improve them according to the S500 thread, it did improve them but the sound still fell short for me, especially compared to the ES10, so I'm disappointed in the performance of the S500 and never use it, but I still love the JVC FXD80 (IEM).
At some point I decided to try the velour pads on my ES10 and they fit perfectly, so I just assumed the ESW9 listed in the ebay advertisement had the exact same dimensions.
I looked very closely at the size of the aftermarket velour pads and the ES10 pads, since they are the same dimensions and the cloth material of the grille is pretty similar (it's like a very thin sock versus a stocking), I'm actually a little perplexed at how the velour alone in identical dimensions can reduce the bass frequencies so much.
At another time when I listened to a mint ES10 quickly in a store, it sounded so different to mine I took my own ES10 there the next day, it was only when I pushed the cups closer to my head on the mint ES10 I could feel assured they were actually the same headphone (not a secret version 2 or something). The mint ES10 with stiffer pads sounded a lot thinner.
With the new velour pad switch I can't say it sounds perfect since it's a little more misty now with less contrast and I miss the feel of leather, but the velour is very comfortable and the sound has become more addictive and suitable for extended sessions.