Alpinestars Nucleon KR-3 Protector ::

Alpinestars Nucleon KR-3 Protector

The Nucleon range of road protection features a superb anatomical fit and comfort. Constructed with innovative protector plates which are lightweight and feature a high performance polymeric blend for protection. Featuring new, modular rib protectors for strategic protection in a vulnerable area, the Nucleon KR-3 Protector offers excellent performance under an outer leather or textile garment.


  • Back protector CE certified to EN 1621_2:2014 LEVEL 2.
  • Back protector constructed in three waist-to-shoulder dimensions in order to cover all the body size.
  • New structured back shell plate is constructed from a high performance polymeric material blend for optimized flexibility and excellent weight-saving.
  • Protection incorporates hybrid construction with lattice shell with a new viscoelastic PU foam compound.
  • New single-injected lattice structure shell constructed with ergonomic design to absorb high impacts and allow maximum breathability and air flow.
  • New soft viscoelastic PU foam compound on the central spine area for fit, comfort and impact absorption.
  • Convex design on the central hard shell provides highest level of protection of the spine.
  • Horizontal flex channeling for adaptive fit in all riding positions.
  • New adjustable rib protector constructed from a high performance polymeric material blend for additional side protection.
  • New shoulder blade padding extensions to protect the impact areas.
  • Waist adjustment for customized fit and slim vented kidney belt for added position stability and security.
  • Adjustable and detachable elastic shoulder straps via snap fit system to allow a more comfortable use of the protector.
  • Compatible with the Nucleon KR-C protector.
  • Compatible with the Nucleon KR-TB protector.

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Sizing Information

These back protectors are sold by your body height and here are the recommendations from Alpinestars:

Product Size Height Range
XS 5’4 1/2” – 5’6 1/2”
S 5’6 1/2” – 5’7 1/2”
M 5’7 1/2” – 5’10”
L 5’10” – 6’
XL 6’ – 6’3”

Note: This back protector has a slightly different size chart from the other Nucleon BPs introduced a couple years ago. Not sure why, but the difference is only slight.

Just to give you an idea of height, the size large we used for our photo shoot is 23.5” tall overall. the photos were done on our XL size mannequin Dewey.

Our Two Cents

The Alpinestars KR-3 back protector is similar in function to the other “stand alone” back protectors which are meant to be worn on the body, and under any race suit or jacket. The waist band and the shoulder straps keep the back pad in place without relying on being affixed to the jacket or suit. But his back protector adds extra protection in the “love handle” area that the other back pads don’t. You can see the protectors that are attached to the wide waist belt. Alpinestars says these are “rib protectors and they do reach up toward the ribs but are mostly positioned on the side of the torso over the hip bones. Call it what you will, but generally they cover the side of the torso.

The back protection of this model is most similar to the KR-1 which is made of a flexible and pliable base material with a much firmer stiffener piece overlaid on the back. We recommend this type of back pad for those needing the highest level of protection… those involved in aggressive sport riding and racing. Like the others, this one is also compatible with the Nucleon KR-C chest protector and KR-TB tail bone protector (see those options below).

As of this writing, I’d say this back protector along with the accessories would be the most comprehensive and full-coverage back and torso setup we offer! :: Paul, 10-04-17

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