This is worn over a hat with a brim to block sunlight. It can prevent heatstroke by protecting the neck from direct sunlight. Simply slip it on over a hat with a brim. The size is adjustable with a strap. The face can also be covered with fabric. It's great for outdoor work, and it's compact, so you can carry it with you for hiking, climbing, fishing, and other activities as needed. The hat in the photo is not included.