Goku's Golden Diadem 001
Golden Diadem 【金鈷 Kinko】 (Sai. Vol 3 - Continuous)

☆ The gold ring around Son Goku’s head is his youkai power limiter. It differs in material from those sold over-the-counter, and can apparently be made only by a god’s hand (and Genjo Sanzo). When Goku’s mental state reaches the maximum level of confusion or anger, the limiter can’t keep up with his amplified youkai power, and shatters. Unrelated to the youkais’ rampaging, Goku loses his sense of self and all reason when he returns to his essential form of the Seiten Taisei and he is unable to suppress his released power. In the Desert arc, Goku removes the diadem with his own hands.