13x21_3/4x1 Exact MERV 7 Plus Carbon AC Furnace Filters 6 Pack Controller • Inside gradation to verify

• Inside gradation to verify water level

UVSpec: 54 μmol/s

162 cells per sheet

and praying mantids and do not harm earthworms

13x21_3/4x1 Exact MERV 7 Plus Carbon AC Furnace Filters 6 Pack Controller • Inside gradation to verifyNordic 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