Home > BROWSE STORES > AllergyBuyersClub > BRANDS > Guardian Furnace Filter and Air Conditioner Filter Guardian Electrostatic Mfc: Guardian Furnace filters and electrostatic air filters that are permanent and washable. These air filters can serve as air conditioning filters and heating furnace filters. How to Measure for the Right Size Filter NOTE: Actual furnace filter sizes are 3/8 les Part# GUEFFURN SKU: GUEFFURN Price: $179.95 Price Drop Alert   Buy Now   Note: Displayed Prices are subject to change without notice. Please Click on the Buy Now link in front of the item to check current price.