Fit this over your Twin Air Filter when you’re riding in severe conditions such as heavy dust and sand. This coarse foam pre-filter, oiled for maximum benefit, will act as an additional layer of protection and extend the service time between filter cleanings. DUST COVER HONDA CRF250R 22-24 CRF450R 21-24 CRF250RX 22-24 CRF450RX 21-24