20x20x4 (3 5/8) Furnace Air Filters MERV 10 Pleated Plus Carbon 6 Pack books-&-videos 36 x PotPro™ | 3

36 x PotPro™ | 3 Gallon

The main Chamber holds up to 1/3 full (approx 2 lbs

- Kills and controls fusarium

Some cultivars and growing conditions may require higher doses of Calcium

20x20x4 (3 5/8) Furnace Air Filters MERV 10 Pleated Plus Carbon 6 Pack books-&-videos 36 x PotPro™ | 3Important 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 20x20x4 filter