Replacement prefilter to fit certain Honeywell electronic air cleaners. Note that this part fits models with 1 collector cell. If you have the air cleaner model that has 2 collector cells you need part number 198442 also available from us. Aluminum mesh prefilter is roughly 3/8 thick. 12 x 19. Measure your existing prefilter to verify this is the proper part number if you have an older model.