Models RMDD3004EX, RMDD3604EX and RMDD4804EX offer you choice of exterior blowers ranging from 660 to 1620 Max Blower CFM or in-line blowers from 320 to 1540 Max Blower CFM (blower required and sold separately), Heat Sentry(R) adjusts speed of blower to High automatically in case of excess heat, to prolong product life, Chimney rises over 9-1/2 inches when activated, ideal for large pots and pans, Optional remote control will activate down draft from an alternate location (RMDDRBK sold separately), Powerful blower to quickly pull smoke and cooking odors out of the air, Easy-to-use rotary control lets you adjust the fan speed, Retractable downdraft hood rises from behind the cooktop and retracts when not in use, offering a seamless design for your kitchen, Dishwasher-safe filters are easy to remove and feature a stylish brushed stainless steel appearance for a professional look, Unique ducting capability allows the internal blower connection to be ducted to the left, right or downward (from left to right)