Nispira 3-in-1 high quality, effective HEPA filters with activated carbon help to purify the air by capturing particulates. Particles 0.3 microns and larger that pass through the filter are captured to help maximize comfort and freshness. Activated carbon eliminates smoke and other household odors from cooking, pet and chemical. Preliminary filter in fiber to capture large particles such as hair, dust and debris. These filters are compatible with the following Holmes air filter units: HAP242-NUC, HAPF300AH-U4R, HAPF30AT-U4R, CAP531-U, CAP529-U, HAP240, HAP242, HAP412, HAP422, HAP424, HAP706, HAP716, HAP9240, HAP9242, HAP9412, HAP9414, HAP9422 and HAP9424. It can also be used with the following Bionaire units: BAP260, BAP815, BAP825, BAP9200, BAP9700 and BAP520. It measures 1.2 x 10 x 4.6 inches and comes in a pack of 2. We recommend replacing your air purifier filters every 6 months to maintain effectiveness and efficiency. This is not a Holmes OEM product. Holmes is a trademark or registered trademark of its respective holder. This product is not endorsed by Holmes. Any use of the name or model Aer1 designation for this product is made solely for purposes of demonstrating compatibility. There is no affiliation with the brand.