According to JIS standard, unless M8 nut is 13 mm, it can not be turned. Both mouth wrench, glasses wrench and socket (hexagon) were all arranged with KTC. I will use KTC for placing large torques or places where I can lick.
When replacing the plug of a car, I bought it for the desorption of a bolt that needs an offset in the narrow place where normal ratchet etc etc does not enter (when replacing plug of Subaru car). Very easy to use and satisfying.
It is replenishment of the glasses wrench lost by the set item. It is good because the manufacturer's goods are cheap and can be bought from one. If there are things you want with a tool, I will check again.