Aprilaire / Space-Gard #413 High Efficiency Filtering Media (2-Pack) Fits the following Aprilaire Air Cleaners: Model 2400 after upgrading with #1413 Media Upgrade Kit Model 2140 after upgrading with #1413 Media Upgrade Kit Model 1410 Model 2410 Model 3410 (new premium model with electronic control) Model 4400 (old premium model with electronic control) Newly designed media features: Traps and removes 75% of virus-sized particles (.3 to 1 micron) and over 90% of dust-sized particles (3.0 to 10.0 microns). Traps and permanently removes over 90% of pollen, mold and spore sized particles (3.0 to 10.0 microns). Collapsible media with self spacing pleats installs in seconds. Media replacement is recommended after one to two years depending on air flow. SelfSeal dramatically reduces air bypass, improving filter performance. Rated MERV 13 Airflow Capacity up to 2000 CFM Maximum No pleat spacers - media slides right in!! Instructions: 1).  Turn home thermostat mode to "OFF' and fan mode to "AUTO" 2).  Remove Air Cleaner door 3).  Remove dirty filter 4).  Expand clean filter 5).  Install new (clean) filter with Air Flow arrow pointing toward furnace or air handler.  Align filter top and bottom rails and slide into place.  Replace door 6).  Press reset on air cleaner control 7).  Return home thermostat to original settings