Building is not robust, but it is a product with high cost performance. Since the manual is a bit hard to understand, I reduced one star. Although it has nothing to do with the product itself, there is a problem with the display of the MonotaRO site. (1) This is an important issue as it is information on the size of the attachable window (incorrect description of the attached drawing is correct). Takao was 50 mm, but 50 mm, it was a dangerous place (another room was out of place because it was inappropriate in this area, so we stopped purchasing additional items). (2) Specifications of the description below are wrong Ventilation air volume is greatly different from the specifications of the manual attached to the product. Site: ventilation air volume (m 3 / h): 50 Hz: 680/60 Hz: 720 Attachment manual: ventilation air volume (m 3 / h): 50 Hz: 500/60 Hz: 510 This is bad. (3) Although the manufacturer's part number is not shown on the extension panel set, it is a detailed story, but the sense of trust at the time of purchase is impaired. Since the product lineup and price of MonotaRO has been very useful, I posted it with expectation for further improvement and development in the future.