Details with prices are included in the above links.
Please take note, these are NOT the cheap filter socks you find all over the internet. These are top quality, polypropylene filter socks with stitched seams, not glued. Properly maintained and rotated with a number of additional socks, these socks will not degrade after a few washings like the cheap version, they will last for many, many months.
I agree with Russ
The socks that he sells have black plastic rings that hold up much better then the white ones that you see, you would know what I mean if you wash your socks in a washing machine. Also the felt material is thicker then the other branded socks that I rotate.