The Broan-NuTone RMDD3004EX RangeMaster 30-inch Downdraft Shell is designed to be used with your choice of 8 external blower options (4 exterior blower options or 4 in-line blower options all sold separately). External blowers are located remotely, outside of the range hood, and come in two versions, exterior and in-line. Exterior blowers are located on the outside roof or wall of the house and in-line blowers are located within the house structure. The compact design of the shell is installed directly behind the cooktop and is specifically compatible with most conventional and commercial style cooktops. Stainless steel construction on all exposed surfaces provides a durable finish and an unforgettable professional look. The chimney rises over 9-1/2 inches when activated, ideal for large pots and pans. The infinitely adjustable control is designed to provide convenient access to govern the blower speed and the Heat Sentry adjusts the blower speed to high when excess heat is detected.