The ELECTRA SILVER 8800 is designed to provide the highest arrestance available for the majority of furnaces and air Conditioners. The 0.12 inch W.G. initial resistance of the Electra Silver 8800 will perform best in systems configured with 1 square foot, or more, of filter area for each ton of air conditioning. Two layers of woven monofilament polypropylene with integral anti-microbial material provide 10 times more filtration than a disposable fiberglass filter. The deep loading center layer of non-woven polyester allows the Electra Silver 8800 to prolong the time between washings.