Original price was: £89.99.Current price is: £85.49.

The back protector insert is a full-length back protector, about 22% longer than regular back protector inserts. The Nucleon Flex Proi is compatible with all Alpinestars’ sport and touring jackets that have released since Spring 2022, as all jackets have a double pocket to insert either a regular or longer back protector insert.


The extremely lightweight Level 2 CE and UKCA certified Nucleon Flex Proi Full Back Protector Insert features a highly ventilated hybrid of Nucleon Cell and Nucleon Flex protectors for the optimum balance of force dispersion and flexibility, with a soft-touch 3D mesh liner for enhanced rider comfort. The goal of the Nucleon Flex Proi is to deliver full-length coverage in terms of protection like a fixed back protector does, but with the practicality of an insert.

1. In terms of construction, the hybrid technology blends the best properties of Cell and Flex technologies to create an ultra-protective solution that delivers premium, breathable performance, and maximum flexibility.

2. The protector has an ergonomically contoured dual zone outer shell constructed from an advanced polymeric blend with a solid Cell structure core framed by a moreflexible 3D Cell structure as the first line of defense; this is reinforced even further with the Nucleon Flex technology layer on the central back zone.

3. The protector is backed with a breathable soft-touch 3D mesh liner for maximum airflow and optimum rider comfort.


  • Back Protector: EN 1621-2:2014 Level 2 (T+ & T-).


  • The super lightweight back protector insert is developed in three waist-to-shoulder dimensions in order to cover all body sizes.
  • High performance polymeric material Cell and Nucleon Flex structures for optimized flexibility and excellent weight saving properties.
  • The back protector’s design changes from the center towards the outside providing the perfect balance between energy absorption and flexibility.
  • Soft comfortable 3D mesh on the body side of the protector offers breathability and rider comfort.
  • Snap button compatibility for quick and easy use with Alpinestars suits and jackets.
  • Rigorously tested and certified to for proven performance in extreme temperatures.