... .With Zinc plated or stainless steel fan blade. 3Can be used in the ... close, windproof, rainproof and dustproof. 5Newly punch forming fan blade, reasonable angel and reach the max. air flow ... process: noise test, vibration test .concentric performance test, fan blade turning speed test, input air teat and vehicle ... effect. 10belt type B,thicker and durable ,double life time MUHE Exhaust Fan For Workshop