1, outside housing totally enclosed design: outside of the cabinet is made of high temperature resistance of nano flame retardant PP make housing under the high temperature of 130 degrees long-term deformation not aging.2, double totally enclosed design waterproof effect is much better. Internal hidden type wiring design: housing internal is also an enclosed whole, all wires, some hidden wires into full package, ensure to be both safe and clean.3, double wind mute: large rotor design the air more, combined with the Archimedes law mute type air duct design, the noise is small.