Top-notch product - effective, efficient, quiet and attractively styled. I have now purchased 4 Alen air purifiers over the past two months (2 BreatheSmart Flex, 1 BreatheSmart Classic, 1 BreatheSmart 75i). The units have truly transformed the air quality in my home. Very convenient to simply clean the pre-filter with vacuum attachments. I have a number of pieces of dark wood furniture throughout my home, and the reduction in visible dust since I have employed these units is truly remarkable.