Most commonly known by its Japanese Name Tonfa
In Japan the Tonfa originated more as a farmin tool, in China the Guai is more of a Crutch.So they are different types.Like I said before the most common one is the Tonfa seen in Kobudo and sometimes the Guai in some
local Shaolin Circles.
I know of a Double Tonfa Form in Pak Mei but its pretty much never shown,