1.High quality exhaust fan 2.With Zinc plated or stainless steel fan blade. 3Can be used in the workshop,farm,garden 1The ... open and close, windproof, rainproof and dustproof. 5Newly punch forming fan blade, reasonable angel and reach the max. air flow, ... quality test process: noise test, vibration test .concentric performance test, fan blade turning speed test, input air teat and vehicle efficiency ...