【Fit】GEAR Shaft fis6156 ["Normal"] ["Spin"] 6 (35.0mm) Clear 's Japan Review

We are pleased with the increased strength compared to the previous product and the increased variation in length.

An improved version of the Fit shaft, the Fit shaft gear.
CosmoDarts claims that it is "very strong" but it breaks quite easily.
It is not a cheap shaft, so if it breaks, it will damage your wallet quite a bit.
The lengths range from #1 to #8, normal, slim, and medium thicknesses, and spin and lock flight retention types.
The fact that there are so many choices puts it far ahead of other shafts.
The small number of component parts means that even if you use the spin type, it does not shake catastrophically and you will not be stressed.