Alpinestars Vest Nuc Flx ProBack Protector Ergonomically contoured dual zone outershell Advanced polymeric blend with a solid cell structure core Solid cell core framed by a more flexible 32 cell structure Nucleon Flex technology layer on the central back zone Divided Chest Protector Unique new longer length for more protection coverage in critical area Lightweight, ventilated and ultra comfortable technology Rigorously tested and certified for proven performance in extreme