Chanur - 4/21/2018 16:04 Have a new furnace that requires hi-flow air filters... HVAC dude says I cannot use the 16 x 20 x 1, 3M filtrete filters because they are only good for units pushing 1100 cfm. Mine is a 1300 cfm unit. Koch filters came with the furnace and I ordered a dozen but they are slow in coming...thanks...