(One Point Tip) This mask is common to all masks, but it is particularly prone to fogging due to the film that adheres to the glass surface during the manufacturing process. By removing the film on the inside of the mask with a melamine sponge or a fine abrasive particles, it is difficult to fog. (Be sure to polish the inner glass surface of the mask and remove the coating). Furthermore, you can expect a better effect by using the "anti-fog" dedicated for diving masks before using it every time.