Replacement filter insert fits Aprilaire and Space-Guard furnace model numbers 2400.
Also Fits Lennox Models: PMAC12C PMAC12-C PMAC-12-C
Replaces original Space-Gard part number 401.
This is an accordian-style standard filtration replacement that expands to fit inside your filter frame assembly.
Original part number; SG4, 401.
Aftermarket, NOT made by Lennox