Last one first: Yes, they are both Japanese. The metric thing would also apply to any European heli, and may even apply to USA helis like the X-Cell (I'm not sure).

A 5.5 mm nut driver is not a rachet, it's like a screw driver with a socket head at the end for a 5.5 mm nut. You will find that this is the most common size nut used in helils, and that your trusty socket set does not have half sizes (1.5, 2.5, 3.5, 4.5 mm, etc.) Thus, you really need the special nut driver.

I got my combo ball link driver and glow wrench at my LHS. Come to think of it, that might be the one Century tool I still use :stupid: