18x27x1 Exact MERV 7 Plus Carbon AC Furnace Filters 6 Pack nutrients Accessible nitrogen is the key

Accessible nitrogen is the key to a plant having a strong and vibrant internal structure

Relative humidity range: 0%-100% RH

When full of water: 11

Use 1/4 teaspoon per gallon of water

633 and the FS+UV to create a custom light spectrum for a start-to -finish combination

18x27x1 Exact MERV 7 Plus Carbon AC Furnace Filters 6 Pack nutrients Accessible nitrogen is the keyNordic Pure Custom MERV 7 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