1. economic design requires fitting, 2. compact and space-saving design This filter has four series,"*" stands for different classes, it is 7, 5, 3 1;"#" stands for optional accessories;class 7: accurary: 1μm,bottom oil≤1ppm;class 5: accurary: 0.01μm,bottom oil≤0.01ppm;class 3: accurary: 0.01μm,bottom oil≤0.001ppm;class 1: active carbon filter,bottom oil≤0.003ppm;ModelAir dischargeAir Entrance & ...