20x20x4 (3 5/8) Pure Carbon Pleated Odor Reduction Merv 8 Furnace Filters 6 Pack hydro-x 1 Phase) are built to

1 Phase) are built to last

Spectrum : Full Spectrum

Dosages depend on your style of growing

Outstanding results controlling powdery mildew

Bloom A works in precise synergy with Grow A

20x20x4 (3 5/8) Pure Carbon Pleated Odor Reduction Merv 8 Furnace Filters 6 Pack hydro-x 1 Phase) are built toImportant 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