This aluminum cap is designed to cover the ears and the back of the head, providing protection for the cerebellum and midbrain. I am offering this because commercially available products do not cover enough area, and I am concerned that they only protect the cerebrum. (See image 2) To ensure a proper fit, please measure: * The length from the top of your head to your ear * The length from your left ear to your right ear and provide these measurements in a comment. This will be a custom-made product. I have not sold online before, but due to numerous requests, I will be accepting a limited number of orders exclusively on Mercari. Thank you for your understanding. - Material: Aluminum - Features: Can be used as a hat to protect against electromagnetic waves