A small sanitary Filter that filters down to 023 micron at 99.99 percent efficiency. Both 1/4" and 3/8" tubing will attach and it will fit snugly in any standard stopper as well. Perfect for aeration or oxygenation systems to Filter out any contaminants. Store in Ziploc bag in a dry place with minimal moisture exposure. Discard if their are any signs of discoloration. There are two sides to the Filter an "in" and an "out". the direction you use doesn't matter, however, you want to take note of which way you first push air through it and always keep it that way. There is an arrow on the edge of the Filter housing that we use to keep the air flow going one direction when using it.