For Sale: Stainless steel Pre-Filters. 12mm & 16mm

[PC1]

I got my hands on a small group of these Pre-filters I have 12mm and 16mm. The price on them is only $6.50 ea $6 ea if you buy 2 or 3 for $16
These are basic Pre-filters but will do the job just fine. $5.50 for a small flat rate box.
12mm

16mm

 

[sanchezkk]

I'm a newbie just in the beginning stages of my first cycle (fishless). How would someone use these, and what are they used for specifically?