E-Z Flow Air Filter, MERV 4, 12 x 12 x 1-Inch, 12-Pack Pack of 12 disposable UL Class II rated air filters designed for protection of furnace and central air units MERV 4 rating: Removes household dust, pollen, and lint Continuous chipboard design guards against corner separation while the one-sided metal media retainer adds to the filter strength Each filter maintains efficiency for up to 30 days. Length- 12 inch. Width- 1 inch Compatible with HVAC systems requiring filters sized 12" x 12" x 1"