... oil free air compressor piston 4kw WW5512 : Feature:1.smart,and lively structure,with patent design2.excellent layout,light weight3.low cost,low air ... air filter with patent technology,make sure clean air,and low noise.2.fan wheel:arc vane,supplying extra 10% cooling ... cover:Adopt aluminium alloy material,increasing air displacement.Photos: oil free air compressor piston 4kw WW5512