industrail exhaust fan 1)saving energy 2)strong wind power 3)convenient to move industrail exhaust fanColors:yellow ,red, blue, ect. ... Size:8" 10"12" 14"16" 18" 20" Main material: shutter: 7pcs dia-cast aluminum alloy,fan ... design,special manufactured for underground cable maintainance,shipping making,exhaust for fire fighting, piping construction and in other ...