Constructed of galvanized steel sheet 0.9 mm . Thick , for frame , jambs and blades , high strength structure , blades can be adjusted automatically from full open to full close in opposed pattern for high effictiveness in air volume control performance . The electric actuator , wiring and terminal for automatically adjuating the blades are also completely equipped , one type ( MD ) . Applications for mounting to duct line , building sidewall or shaft for control volume of supplied , exhausted , fresh or pressurized air automatically .