20x25x5 (4 3/8) Lennox X6673_X6675 Replacement MERV 10 Air Filters 4 Pack Chemicals This tester includes features such

This tester includes features such as a replaceable graphite electrode

Designed to be used indoors

2 RAW Silica - 8 oz

Check out our Mini Mixer if using a Flexi-Tank

Day and night setpoints adjustable from 20% to 90%

20x25x5 (4 3/8) Lennox X6673_X6675 Replacement MERV 10 Air Filters 4 Pack Chemicals This tester includes features suchImportant Note: Almost ALL furnace filters have a different "actual size" than the nominal size printed on the air conditioner filter. It's best if you measure your air filter for the EXACT size and compare it to our "Actual Size" and then you can be sure your A C air filter fits! With the 4" and 5" air filters there is a wider variance between the nominal and actual size depending on the manufacturer. We also carry 4 7 8 and 5 1 4 inch depth filters,