1. According to the baby's body design, comfortable and can adjust the length of the head circumference. 2. When a baby learns to walk, run and crawl, the baby falls easily. This product can effectively reduce the impact of protecting the baby's head when he falls. 3. Breathable, does not worry about sultry when in summer. 4. Inner material is a black environment-friendly breathable and sweat-absorbing mesh sponge: with the advantage of shock absorption, shock resistance, breathability and gentleness; outer surface using environmental protection velvet: with comfortable, sweat absorption, anti-static characteristics.