This is the bolt used for mounting the M12 soulplate on the M12 boot. You can also use these on other skates ofcourse that have M4 soulplate thread.

More info on how to mount this soulplate can be found here:
https://www.thisissoul.com/blogs/custom-tutorials/oldschool-roces-m12-fco-conversion-to-ufs

The thread is M4.

Will fit perfectly in any other soulplate that uses M4 thread

M = 4mm
L = 7mm
X = 8mm