Let me say first that this is a fork service tool. Adjusting the preload on the bike is not what it was designed for.
It is used to hold the preload adjuster when you remove the whole cap from the cartridge.
It is also used to remove the bottom of the cartridge to change the valving. (I’ll have a hardwood holder for the cartridge available soon.)
It fits most KYB forks, but no Showa ones.
They are made from 0.060″ “Full Hard” Series 400 magnetic stainless…incredibly strong, it’ll never wear out. Seven inches long overall.
Best used with a rag wrapped around the handle to utilize your muscles best: