Sorry did not mean to dampen your mood... but I saw the description stated 16mm in diameter, which would seem to me to be those for earbuds. But I do hope it turn out to be what you hope for. Fingers crossed.
Did you try to ask the seller before you bought?
further check showed they do stock other foam like these:30mm Foam Pad Ear Cover for Sony Creative Headphones on eBay (end time 27-Sep-09 19:48:31 BST)
I measured my portapro's sponge and my KSC 75's... they seem to be around 50mm in diameter across.
Maybe you want to contact them to clarify or change order?