... 1.with scientific trumpet design,low noise ,large air flow and strong force of drawing air.2.Synthetical PVC shutter using ... air downstream,anti-oxidation,light weight,ametabolic.3.flexible open and anti-air-back.4.Aluminum alloy wheel hub : light weight ... ,6.plastic fan blade: high strength,ametabolic,non-fractured,beautiful and durable.7.special trumpet fan direct type motor.8.plating ...