The 500 PSI Mask Defog is the best selling mask defogging solution that is widely offered on markets. 500 PSI Mask Defog is a good mask cleaner, it is a gel type solution that functions as a protection over the water and moist that might interfere to the view from the snorkels or masks. In addition, the 500 PSI Mask Defog is excellent in providing a crystal clear vision. Since it is a thick gel solution, it can prolong the mask defogging protection into several usages.