Air FilterTWIN AIR CLAMP-ON BACKFIRE AIRFILTER Ø 73MM FOR POWERFLOW-KIT YAMAHA Dual-bonded foam design filters out even the smallest dirt particles, while allowing more airflow than two separate layer filters (flow bench proven).Flat foam sealing ring provides a secure seat against the airbox, even in the worst riding conditions.Twin Air filters are slightly smaller than stock, making them easier to change while increasing dead air space around the filter for better performance.Backfire filters (FR) include a laminated layer of backfire-retardant foam.Pre-Oiled (X) filters are pre-oiled with Twin Air BIO Foam Filter Oil using state-of-the-art filter oiling machines to provide the ultimate consistency in pore coverage.Supermoto (SM) filters are built with Twin Air’s Dust Cover material for added airflow.Washable / Reusable (reusing a TwinAir filter 40-50 times is common).High Quality (assembled by hand and inspected for a perfect fit).Packaged in a resealable bag.Note: Replacement filter for PowerFlow Kit 1011-1988