+ Black silicone skirt blocks skirt light from reflecting off the lens and reducing visibility.
+ The lenses are tempered glass to resist scratching and allow thorough cleaning.
+ + + IST Corona is one of the very few masks available with positive diopter lenses, and maybe the only one available with glass positive diopter. Get a spare mask with standard lenses and save a bundle when your optical mask gets a broken buckle or the cockroaches get an opportunity and eat the edges of the water seal.
- You must thoroughly scrub the new lens with toothpaste or a paste of baking soda and water to remove the coating on the lens or it will be plagued with fogging. (Note: If you do this to a PLASTIC lens, like SeaVision's, it will be ruined!)