These rivet-on flares are reproductions of Nissan 240Z G flares but extra-wide to fit larger wheels. They are shaped to suit the 240Z/260Z body, but are flexible enough to suit many other cars too.
On a 240Z they add around 48mm extra width at the front and 55mm at the rear (measuring from the outer edge of the flare to the outer edge of the factory guard).  At the bottom of the flare the fronts are around 740mm (inside measurement) and the rears are around 790mm.