These seem like quality relatively thick silicon flaps. Single layer. Original de-clumper design was two layers I believe.
I got a couple of these as a backup since I was thinking of modifying the original one in my grinder (or one of these) and see if it helps with the inconsistent retention and prevention of fines with the DF64. I think gently pumping the bellows while it's grinding may also help with ensuring there's a smooth flow and particles are not getting re-ground into finer particles.