16x20x4 (3 5/8) Pure Carbon Pleated Odor Reduction Merv 8 Furnace Filter 1 Pack BVV 1/2" grommet

1/2" grommet

for maximum portability and ease of use

or seedling trays

but shifted ratios on the NPK to allow for the 2-4 week vegetation time that indoor growers are accustomed too (versus the 2-3 month outdoor vegetation time)

Hammertone material provides better diffusion and light penetration

16x20x4 (3 5/8) Pure Carbon Pleated Odor Reduction Merv 8 Furnace Filter 1 Pack BVV 1/2" grommetImportant 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 16x20x4 filter