Purolator HE-40 18x18x1 Merv 8 Pleated AC Filters and Furnace Filters High Dust Holding Capacity Actual Size: 17-3/4 x 17-3/4 x 3/4 $6.48 Each - 1 Case of 12 Total $77.76 The Purolator HE-40 Provides 90-93% Average Arrestance and Maximizes Dust Retention Capabilities