Our Accumulair Gold 18x25x1 air filters for your HVAC air conditioner or furnace contains a unique synthetic media that provides high-efficiency filtration without comprising your airflow. Up to 20-times more efficient at capturing allergens than ordinary fiberglass filters. Uniform pleat shape enhances dust holding capacity and maximizes air flow. Heavy duty construction frame prevents airflow bypass. The electrostatic pleated media is made up of co-polymer micro-fibers that are hydrophobic which means the filter does not absorb moisture and will not support the growth or spread of harmful contaminants. To increase durability the pleated media is laminated to a metal backing that is recyclable. This filter is equipped with media tested to perform at the Minimum Efficiency Reporting Value of 8 - (MERV 8) by an independent lab according to ASHRAE Standard 52.2. MERV claims are to be used as a guide for general comparison and not as a specification. Made in USA!