RCXII and RCXII-SF relief or intake ventilators feature low contour spun aluminum hoods for an attractive appearance. They are designed to exhaust or supply air from or to an enclosed area without the need for a power operated fan. Available in two styles, these fans range in sizes from 6 to 36". The RCXII has a curb cap found on most roof ventilators and must be mounted on a roof curb.