Size Note: Minor differences between the helmet's size label and the website description (e.g., physical label: M: 55-58cm vs. product description: M: 54-57cm) are normal and do not mean you received the wrong item. This is because the label displays standardized production parameters (which ensure compliance with various safety standards) that may not perfectly match the actual wearing experience. The size range we provide is our recommended fit, and we welcome your feedback and any questions you may have.