FZ6 Fazer Swing Arm Nut size?

[Grahamm]

I wanted to remove my swingarm, but the largest socket I have is 24mm.

I tried to measure it and seemed to get a size of 26mm, so I bought one, but that is just too small!

So can someone tell me if it's 27mm or 28mm before I go out and buy another socket that's the wrong size...