Muc-Off Anti Fog Treatment: 32ml Spray. Muc-Off Anti-Fog Treatment uses cutting edge moisture absorption technology with an anti-mist formula to create a transparent micro-thin coating so your ride is never cut short by foggy goggles. Anti-Fog Treatment lasts up to five days and if you spray on the outside of your swim goggles or sports glasses the anti-mist formula will help rain bead off to make your ride that much safer. With this long-lasting formula your goggles will be fog free for up to five days.