21x27x1 Trane Replacement MERV 12 Plus Carbon AC Furnace Filters 6 Pack Paleo Bloom allowing the user to affix

allowing the user to affix ducting so that an exhaust fan can extract hot air

and you're set

There is specific label for California use that is more restrictive

It is designed for high PPFD cultivation practices

21x27x1 Trane Replacement MERV 12 Plus Carbon AC Furnace Filters 6 Pack Paleo Bloom allowing the user to affixNordic Pure Trane Replacement MERV 12 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