Filter. Air Yz 450 F 152221Standard Air FilterTwin Air dual stage filters are the choice of top factory teams and riders worldwide Dual bonded foam design filters out even the smallest dirt particles, while allowing more airflow than two separate layer filters (flow bench proven) Slightly smaller than stock, making them easier to change while increasing dead air space around the filter for better performance Flat foam sealing ring provides a secure seal against the airbox, even