Think Crucial 3 Replacements for 21x23x1 MERV 11 Allergen Air Furnace & Air Conditioner Filter, Pleated HIGH QUALITY AIR FILTER that can replace your furnace or air conditioner's filter. Get back to having a clean air to breathe again! This filter is 21" x 23"x 1" inches. HEALTHIER LIFESTYLE! No one wants breathe dirty air in their home and if you don't clean your air filter that will be exactly what you'll be doing! Replacing your filter will help clean your furnace or air conditioner's air and allow for a healthier lifestyle! This filter helps keep our household dust, pollen and mold spores. SAVE MONEY by using a new air filter! When your furnace or air conditioner has a clogged or dirty air filter it can cause it to work harder which will end up hurting your electric bill! EASY TO INSTALL so you can get back to breathing in clear air as soon as possible! Simply remove your old filter and put this brand new one in it's place! GUARANTEED SATISFACTION because of a 30 day full money back guarantee and a trusted Think Crucial warranty. We are so confident in our products that we have no problem giving you every penny back if you're unhappy with your purchase. You won't see promises like that from big box brands!