Alpine SBFD30 30 Inch Wide Return Air Support Box With Filter Slot

In this case, the return vent filter will be the primary air filter After putting the new air filter in its slot, close the return vent

Southwark FB2128 SKU: 74846 Southwark FB Furnace Support Box with Filter Slot, 20 x 25 x 1 Inch, 21 Inch W x 18 -12 Inch H Ready To Ship! 15 In

return air support box with filter slot Snappy™ SBF36 Return Air Support Box with Filter Drawer, 36x28x15 in D, Steel, Galvanized ; Depth: 15 ; Finish: Galvanized ; Length: 36 in ; Material: Steel ; Width:

return to the feature slot Is this a big deal? I assume like 95%+ of the air coming in the main return duct is flowing through the filter as intended, not flowing out