Not all wood species are suitable for every size hook.
I can insert Japanese style shafts into a wood handle. This makes it possible to use the Japanese sizes :)
Actually it just adds a better handle and results in less fatigue, which allows you to crochet longer or more easliy.
These are for the really small crochet hooks that are very popular in Japan and other places where they like to crochet small.
My handles allow you to actually use the hook :)
Don’t tell anyone, but these sometimes start out as crochet hooks before they become handles.