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
These are basic Pre-filters but will do the job just fine. $5.50 for a small flat rate box.
12mm
16mm