21_1/4x23_1/4x1 Exact MERV 13 Plus Carbon AC Furnace Filters 6 Pack environmental-controllers it is recommended by top

it is recommended by top horticultural experts and ideal for a wide range of plants

creating a more breathable garment that helps prevent heat stress

you can grow with confidence

this duct fan features an EC-motor that is controlled using PWM (Pulse Width Modulation)

21_1/4x23_1/4x1 Exact MERV 13 Plus Carbon AC Furnace Filters 6 Pack environmental-controllers it is recommended by topNordic Pure Custom MERV 13 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