The green valve is not included in your mask purchase, but can be purchased here separately. The green valve can be inserted into your mask and can be rotated over the ventilation holes to create a barrier for cold, incoming air. This is especially helpful for windy days or if you are moving fast. 

The valves do not entirely block the entry of cold air, but can help block a direct hit of cold air to your face. Many customers find they do not need the green valve for their winter time adventure, but if you are going to be outside in very windy or fast conditions they can be helpful. Simply attach to the inside of the ventilator and rotate as needed!