1. stainless steel blade 2. with CE certificate 3. auto open and close ... accuracy, material adopt zinc coat and zinc plate, stainless steel also ok.2. Switchgear automatically windproof, rainproof and dustproof ... : noise test, vibration test, concen-tric performance test, fan blade turning speed test, input air tes and vehicle efficiency test ... service, low price, but good quality. advanced exhaust fan