The crank is made of aluminum alloy, which reduces the weight while ensuring the strength. The crank is processed by precision numerical control, and the cut surface is sharp. Use four nails to fix and lock, stable and not easy to fall off. The inner side of the crank is hollowed out to reduce the weight to reduce the burden of riding.It is not easy to be deformed when pedaling hard, and it has better rigidity and force transmission effect. Material: aluminum alloy body + chromium phase steel shaft. Bottom shaft: 24mm screw-in bottom shaft Length of shaft center: 115mm. Crank + bottom bracket + sprockets. Also, the each additional item means exactly the the same color and size.