These genuine carbon pre-filters are designed to fit the ELECTROLUX air cleaner Oxygen Z 9122, 9124. The aim of the carbon pre-filter is to capture the large particles and neutralise unwanted odours and volatile organic compounds . In combination with the genuine air filter EF 108W, it helps you to improve the air quality in your home. For optimum performance of your air cleaner, we recommend to replace the carbon filter regularly, every 3 months. Do not wash and reuse the carbon pre-filter as it will not work effectively. This pack contains 4 carbon filters. Air cleaner carbon filters reference: EF 109.