The product was introduced and developed in 1999 and launched in large quantities in market in 2000. After years of good sale, it is highly stable and reliable. The case of quality aluminum alloy is durable and resists against deformation and discoloration with a long service life. The unit is of ultra-light and ultra-thin streamline form with low airflow resistance, thereby effectively reducing the fuel consumption of vehicle. The unit may adapt the bus of any roof profile and harmoniously and perfectly blend into one integral whole with the complete bus. It was listed in the key research projects to be tackled in 2005. Breakthroughs were made in energy efficiency ratio, cooling capacity weight ratio and refrigerant filling amount. It is applicable for all buses for public transport, passenger transport and tourist transport.