3-PK ReservePro 4551 (old #4501) 20"x25"x5" Air Filter-Actual Size= 19 5/8" x 24 3/16" x 4 15/16"- 6FM2025 Genuine Generalaire / ReservePro Filters 4551- exact size of 4501 Nominal Size: 20" x 25" x 5". Actual Size:19-5/8" x 24-3/16" x 4-15/16" MERV 11 MADE IS USA PACK OF 3 FILTERS