21_1/2x23_5/16x1 MERV 13 Plus Carbon AC Furnace Filters 6 Pack Lighting With the Bluelab Guardian Monitor

With the Bluelab Guardian Monitor monitoring your crops 24 hours a day and with the ability to set high and low alarms

The built-in temperature sensor ensures every reading is adjusted for environmental changes

Treat your root zone with respect and your other problems will simply go away

Decrease during flowering to keep nitrogen levels accurate

• OMRI Listed and Compliant for use in organic farming

21_1/2x23_5/16x1 MERV 13 Plus Carbon AC Furnace Filters 6 Pack Lighting With the Bluelab Guardian MonitorNordic 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