P84 needle felt Weight: 500g/square meter Thickness: 2.2+/-0.1mm Air Permeability: 16 m3 /m2 ... -shaped structure with a larger filter surface, and always embeded in the surface of other needle felt with different material to ... , good chemical resistance, good air permeability, high filtration efficiency, mostly applied in Cement kiln, Asphalt, Waster Incinerator, coal boilers, etc. P84 needle ...