Protection & Ventilation: OutdoorMaster climbing helmet features a top thickness of 1.7 inches. The thick core design enhances protection, especially against falling rocks and other objects from above. The thickened top design makes the helmet slightly taller, ensuring smooth airflow and reducing stuffiness. PC Shell & EPS Core: Utilizing a PC+EPS in-mold molding structure, this climbing helmet offers lightweight durability, efficient cushioning, and shock absorption, ensuring comfort during prolonged wear. Certifications: EN certified (EN 12492:2012). Ultra-Light Design： The climbing helmet ensures greater comfort during long-term wear, reducing fatigue in the head and neck. Weight: 290g. Size Adjustment Button: Featuring an adjustable system, this climbing helmet can be easily adjusted with one hand to achieve a comfortable fit for various head sizes. Size:20.86"-24". Lamp Clips: 2 front and 2 rear clips securely hold headlamps for outdoor activities like cave exploration and rock climbing, for this climbing helmet.