Horton's WindMaster Revolution is a high-efficiency, hybrid-flow fan that meets the airflow demand of EPA 2010, Euro VI and Tier 4 engines. Designed for compact engine compartments, the fans are available in two sizes: 550-millimeter fans for off-highway equipment and vehicles and medium duty trucks; 750-millimeter fans for heavy duty trucks and some off-highway equipment and vehicles. WindMaster Revolution fans have 20 percent greater airflow than axial-flow fans, significantly lower operating noise, greater efficiency and a similar-size inlet. Compared to radial-flow fans, the new fans have 40 percent smaller depth and a larger inlet diameter, require a significantly smaller space and do not require space for complex fan housing. Compared to mixed-flow fans, WindMasters have more than 15 percent greater airflow, 30 percent smaller depth, greater efficiency and a larger hub section that provides for more fan drive mounting options.