16x21_1/2x1 Exact MERV 14 Plus Carbon AC Furnace Filters 6 Pack reflective-and-greenhouse-films Calcium (Ca) is a critical

Calcium (Ca) is a critical structural component of cell walls

and specific ingredients for large container gardening

bathing your plants in full-spectrum light

Active across varying environmental conditions

The BlackBird is optimized for a 4x4 flowering footprint at 20–24" above the canopy

16x21_1/2x1 Exact MERV 14 Plus Carbon AC Furnace Filters 6 Pack reflective-and-greenhouse-films Calcium (Ca) is a criticalNordic Pure Custom MERV 14 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