1.[COMPATIBLE MODELS]?aThese premium FLT4100 HEPA replacement filter is specfically compatible with AC4100, AC4100CA, AC4150BL, AC4150PCA, AC4150P Technologies Models, compared to Part No. FLT4100 Filter E. NOTE: This is not OEM product. Any use of the brand name or model designation for this product is made solely for purposes of demonstrating compatibility. 2.[H13 TRUE HEPA]?aThese FLT4100 filters are made of H13 medical grade true HEPA filter, which can clean up 99.97% of particles as tiny as 0.3 microns from the air, such as fine dust, pollen, pet dander, lint, hair, fabric fibers, etc. 3.[ACTIVATED CARBON FILTER]-- Our AC4100 activated carbon filters helps attaching common odors from pets, smoking, and cooking, wildfire, etc, providing a fresh and clean environment for your family and helping extend the HEPA filter's life. 4.[COST EFFECTIVE]?aPackage includes 2 x True HEPA Filter and 4 x Pre-Cut Activated Carbon Filter. It's recommend to replace the FLT4100 Hepa filter every 3-6 months and pre-filter every 2-3 months for optimal performance (depending upon your usage and environment).