The bolt that holds down the clutch bleed line on the left side of the engine.. 10mm hex head, 6mm diameter thread, phillips drive.
Or take the interior out of the rear of the Z and you will find many many 10mm head bolts. I think the bolts that hold the front fenders on are 10mm head too. You can dismantle half of the Z with a 10mm socket and a 12mm socket.