20x20x4 (3 5/8) Furnace Air Filters MERV 10 Pleated Plus Carbon 6 Pack books-&-videos Some cultivars and growing conditions

Some cultivars and growing conditions may require higher doses of Calcium

• LED indicators

minutum - East of the Rockies

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

- Kills and controls fusarium

20x20x4 (3 5/8) Furnace Air Filters MERV 10 Pleated Plus Carbon 6 Pack books-&-videos Some cultivars and growing conditionsImportant 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