Nucleon Flex Proi Full Back Protection InsertHybrid technology Alpinestars' Nucleon Cell and Flex technologies providing ventilation and flexibilityErgonomically contoured dual zone outer shellAdvanced polymeric blend with a solid cell structure core framed by a more flexible 3D cell structureNucleon Flex technology layer on the central back zoneMore protection coverage in critical areaLightweight, ventilated and ultra-comfortable technologyRigorously tested and certified for proven performance in extreme temperatures