Gear trains are customized to meet torque requirements and may be furnished in plastic, brass, hardened steel, or a combination of these materials.

They also determine the combination of appropriate materials: steel, concrete, plastic, stone, asphalt, brick, aluminum, or other construction materials.

The plastics-steel combination flame-retardant barn ventilator has the advantages that: first, the plastic container has a plurality of forming changes, high hole rate and good ventilation;