13x21_3/4x1 Exact MERV 10 Plus Carbon AC Furnace Filters 6 Pack ventilation/air-conditioning This will enhance the plants

This will enhance the plants defense against pathogens and keep the root zone healthy and functioning at top efficiency

enhancing its availability in solution and thus absorption by the plant

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as well as for homeowners and hobby growers

For maximum effectiveness and safety

13x21_3/4x1 Exact MERV 10 Plus Carbon AC Furnace Filters 6 Pack ventilation/air-conditioning This will enhance the plantsNordic Pure Custom MERV 10 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