Alpinestars Nucleon KR-2i Back Protector Insert Alpinestars developed the Nucleon KR-2i represents the evolution of the Bio Armor Back Protector Insert. The Italian brand has thoroughly reviewed its back for its jackets and jackets with ergonomic structure, enhanced ventilation, reduced weight and a new resistance levels. With the CE level 2 certification, back Nucleon KR-2i provides a level of protection thanks to its exceptional advanced materials. Nucleon KR-2i is designed to fit the compartment provided for this purpose in the back of the jackets in leather and fabric Alpinestars latest generation. Nucleon KR-2i ensures greater security without compromising your comfort.