The size of the rear hub nut on a Ford Focus varies depending on the year and model. There's no single size that fits all.
You need to consult your owner's manual or a repair manual specific to your year and model of Ford Focus. This will give you the correct size and also detail the proper procedure for removing the nut (which often involves safety precautions like parking brakes and wheel chocks).
Trying to guess the size could lead to using the wrong tool, potentially damaging the nut or your wheel.
