20x25x4 (3 5/8) Furnace Air Filters MERV 10 Pleated Plus Carbon 2 Pack Hydroponics Waterproof—it floats

Waterproof—it floats

which translates to healthier

and Enzyme Blend

achieve maximum quality and quantity

Photocell deactivates CO2 device during night cycle

20x25x4 (3 5/8) Furnace Air Filters MERV 10 Pleated Plus Carbon 2 Pack Hydroponics Waterproof—it floatsImportant Note: Almost ALL furnace filters have a different "actual size" than the nominal size printed on the air conditioner filter. It's best if you measure your air filter for the EXACT size and compare it to our "Actual Size" and then you can be sure your A C air filter fits! With the 4" and 5" air filters there is a wider variance between the nominal and actual size depending on the manufacturer. If you are replacing a 4 3 8 depth 20x25x4 filter