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

Purchase a Furnace Return Air Box return air support box with filter slot HVAC Return Air Filter Box: Custom AC return air duct The project started when I decided to install central air in my house return air support box with filter slot support* the box may be providing to the air handler itself I don't know what's inside the box to hold up the air handler, or

return of the green knight slot support* the box may be providing to the air handler itself I don't know what's inside the box to hold up the air handler, or