There aren’t many times a replacement part actually improves your bike but put one on your bike & you’ll wonder why you didn’t install a NINJA sooner. The bearings are housed in an alloy shell & wrapped with plastic & fibre. This fusion of the three materials provides the bearings a solid platform to sit on & extends their lives. A lot of people would be satisfied with this, but they went even further by extending the alloy shell so the right & left sides lock together. This locks the frame, cranks & bottom bracket together & provides unparalleled stiffness.