Review on GoPro Anti-Fog Inserts: Ensure Clear Vision with Official GoPro Accessory by Jose Perry

REQUIRED FOR GOPRO. Whether underwater or in general. It helps with moisture you can't see. Everything in an enclosed space will fog up as the temperature changes. This helps prevent that from happening and best of all they are reusable. Don't try to replace them with anything else. They are quite cheap and of good quality.