(PLEASE NOTE Minimum Order Quantity is 4) Efficiency Designed to meet the air filtration efficiency criteria required to gain points toward certification in the Leadership in Energy and Environmental Design (LEEDs) Green Building rating system. Electrostatically charged filter media captures airborne allergens smaller than 1 micron! Great for helping reduce airborne allergens such as bacteria, particles that carry viruses, pollen, mold spores, fine dust, and pet dander. Accumulair filter material will not support the development of mold, mildew, bacteria or other microorganisms in normal use. No chemicals added. Accumulair filters are chemical free! Over 30-times more efficient at capturing micro particles than ordinary fiberglass filters. Lasts UP TO 3 months! APR 1950 Rating What is APR? (APR stands for Accumulair Performance Rating. This rating has been established by the manufacturer of the Accumulair Filters. This rating exists to demonstrate the different levels of efficiency throughout the Accumulair filter line. Generally speaking, the higher the APR, the better the filter performs in capturing small airborne particles. This rating system is an internal rating system and applies to Accumulair filters only. )CAUTION: Most air filters are stamped with a size that is NOT the actual dimension of the filter. Example: A 16x25 filter typically measures 15 1/2 x 24 1/2. Please MEASURE your current air filter in order to get the exact dimensions.