ALPINESTARS Nucleon KR-Cell Back Protector - Medium 6504018-13-MDeveloped in three waist to shoulder dimensions in order to cover all body size types Back hard shell plates are constructed from a high performance polymeric material blend for optimized flexibility and excellent weight saving properties Shells are highly perforated for maximum breathability and air ventilation Single injected compound shell constructed with triple layer design to absorb impacts and allow maximum airflow Ergonomic protector plate