No, not the plastic mesh like pre-filter socks. but rather the white cloth/fabric like you get when buying filter/sump socks. I believe they are made of a polyfiber.
I have not looked at Amazon yet, but prefer to find a local supplier if possible.
I use it instead of sump socks. I run egg crate across the sump tank near both ends and put the "sock fabric" in front of it so it catches the crap floating around. The "sheets" are easier to wash and way cheaper than pre-made socks.
My computer screen does not show the Amazon product pic very well, can not tell what it is, but does sound like it.
This seems to be it but 50 microns
http://www.amazon.com/Singed-Polyest...00+micron+mesh