Gecko neck truss tool size

[mickesjo]

Hi again,

I'm going to buy a real truss tool (didn't receive any with the neck) since my metric stuff scares me to death. I have read too many stories about what can happen with tools that doesn't fit perfectly. I'm guessing the Gecko needs a wrench with some, to me, obscure size like 3/16 or similar. What should I order?

Thanks!