By using the top technology to inspect the corrosive particles in the air, the air filters manufactured by Haogd, Co. Ltd. Can ensure the complete cleaning to prevent the corrosive particles from the air inletting the engine. Also, by means of advanced equipments, high quality filter paper with special fiber structures and good filtering precosion, the air filter of Haogd, Co. Ltd. Can be used to reach the goal of highest filering offciency and best dust holding capabilty under the condittion of lowest wind resistance. Therefore, the ongine can be assurde to get the perfoumance of lowest fuel consumption and of highest power output.