Product details: 803 804 805 Fan Shutter Condition: New Efficiency: AFI80% Construction: Bag Filter Filtration Grade :Medium Filter Medium Material:Cotton Porosity:20-25% Place of Origin:Shandong, China (Mainland) Brand Name:Tongxin Weight:1-2KG Certification: CE ,ISO9001,2008 Color: Gray Warranty: 1 year   The fan & filter can prevent rain water entering in the ultrathin filter,the arc structure of surface leaf barrier may avoid rain water enter. The new generation ultrathin ventilative filter Non spinning fibre filtration cushion is used to prevent more than 10micron of dust particle .