12_3/4x21x1 Exact MERV 8 Plus Carbon AC Furnace Filters 6 Pack veg-and-bloom It allows the flexibility of

It allows the flexibility of adding only the number or rings you need as your plants grow

Spider Mites (Tetranychidae) and other soft bodied insects

Increases oxygen and nutrient availability in growing media

activators or catalysts to produce synchronized and accelerated growth under all conditions

12_3/4x21x1 Exact MERV 8 Plus Carbon AC Furnace Filters 6 Pack veg-and-bloom It allows the flexibility ofNordic Pure Custom MERV 8 Plus Carbon air filters are made based on the actual measurements so be sure to measure your current filter to get the EXACT dimensions before ordering. As with all Nordic Pure filters, the effective life of your filter depends on the environment in which you live. We recommend changing 1 and 2 filters every 30 90 days. Our 4, 5 and 6 inch thick filters could last up to 6 months. EXACT MEASUREMENT: Furnace and air condition