These stainless steel or aluminum filters are designed to act as an oil, smoke, and air-borne particle filter while still allowing airflow to be able to reach the piston assembly. They are very popular because baffle filters work great and last a long time in commercial kitchens, restaurants, and industrial settings. Baffle filters help maintain commercial kitchen air quality by reduc... https://www.partsfe.co.uk/grill-parts/baffle-filters