Six frames built against fogging, in two ways. The K153 and the KE9022 carry an anti-fog lens treatment written into the article number itself, the FW in K153-GFW and TK9022-PHFW. The K76, K159, X170 and X2 move air instead: airflow channels through the frame on the first two, vent slots cut into the top edge of the shield on the X170, and multi-hole ventilation through both lens and frame on the X2. All UV400. Fogging catches you on a slow climb in humid air, not at speed.
