2 Perfect Steerable Transfer Carth filters. High static design meets a wide range of applications. Powerful belt-driven forward curved fans. Single refrigerant circuit on 072 and 091 sizes; dual refrigerant circuit on 120-240 sizes. Dual circuit can be field modified for use on single circuit condensers. Single blower on 072 to 120 sizes, dual blower on 180 & 240 sizes.