Breathing in nasty exhaust fumes while riding is bad for your lungs and just plain unpleasant, so that is why we developed the BioLogic Pollution Mask -- heavy-duty pollution protection for the serious urban commuter. Two replaceable activated carbon filters scrub out noxious exhaust fumes while dual inhale ports ensure adequate airflow even when going out on a full sprint. Made from tough industrial rubber and plastic for long term use and easy cleaning, repleaceable activated carbon filters, and easy adjustment head strap for a good fit.