AlpinePure MERV 11 filters are available in 4-inch (211) sizes. MERV (Minimum Efficiency Reporting Value) is an industry standard which rates the ability of a filter to trap particles 0.3 to 10.0 microns from the air we breathe. Most ordinary, inexpensive filters found at hardware stores are MERV 4 or lower—they are simply ineffective in capturing smaller particles. In addition, AlpinePure 211 filters are pleated to increase the surface area allowing for more holding capacity and less frequent replacement.
Qty 1 is a 6 pack