21x23_1/2x1 MERV 8 Plus Carbon AC Furnace Filters 6 Pack dupe 9 inch digital heat pad

9 inch digital heat pad

These grow tents offer waterproof liners

The granules expand instantly when hydrated

It attaches easily to the frame for easy removal

Each 25 ft section comes with 2 large zip ties

21x23_1/2x1 MERV 8 Plus Carbon AC Furnace Filters 6 Pack dupe 9 inch digital heat padNordic Pure Custom MERV 8 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