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

9 inch digital heat pad

The granules expand instantly when hydrated

so feet are more cool and comfortable even as you sweat

It attaches easily to the frame for easy removal

the computer you are already data logging to will need permanent internet access

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