Customers have a handful of options in the 15 x 20 x 1" filter size category: a MERV 4 rated filter, a pair of MERV 8 rated filters, a MERV 11 rated filter and a MERV 13 rated filter.

The fiberglass 15 x 20 x1" panel filter is designed for general air filtration applications with light to medium dust loading conditions. This filter can be used in all types of HVAC systems and can be used as a pre-filter to extend the life of higher efficiency filters. Filter media may be blue or white, depending on the size.

Another option is the MERV 8 pleated filter, which is excellent for high-velocity equipment. The filter is more than 30 times more efficient at capturing micro particles than ordinary fiberglass filters. It features 100 percent electrostatically charged synthetic grade media and has been rated as U.L. Class 2 by Underwriters Laboratories.

Your other MERV 8 option is the Replacement for Lennox 91X24 Filter. This filter is great for helping reduce airborne allergens and lasts up to three months. Chemical free, the filter features a 30 gauge galvanized expanded metal grid and a moisture resistant double wall beverage board.

The MERV 11 Pleated Filter catches and holds more pollen, dust and other particles than standard panel type HVAC filters. It can also last up to four times as long as standard pads or panel type filters, which can dramatically reduce maintenance and labor costs.

Your fifth option in this size is the MERV 13 pleated filter, which features electrostatically charged filter media that captures airborne allergens smaller than 1 micron. The filter won't support the development of mold, mildew, bacteria or other microorganisms in normal use.