Clean Comfort MERV 11 Pleated Air Filter 16X20X4.5 (4pk)

This is a package of 4 filters. These filters function at MERV 11 and are ~4.5 in thick. Most filters labeled 4.5 in thick are actually ~4.375 in thick, this is normal. 

For this thickness of filter we recommend changing your filter every 6-9 months for maximum air flow, best filtration, and least wear and tear on your system.

Something to note is that human lungs filter air at approximately MERV 8 equivilant. Using filters above MERV 8 helps to take the strain off your respiratory system. For people with multiple pets, allergies, COPD or other respiratory issues a minimum of MERV 11 is strongly recommended.