Not all brake rotors are created equal. These rotors are cast to very high material specification and tight tolerances. The slots extend brake pad life by "wiping" the white-hot boundary layer from the disc and pad, increasing braking efficiency and extending pad life, and they have ramped edges to cut down on noise.
The rotors have a zinc plating to keep the rotors from rusting outside of the pad contact area. This is friendlier for pads than cadmium. Factory size, these are a direct replacement for stock parts. Sold in pairs. Fits 1994-02 US cars with the standard brakes, not compatible with 2001-02 Sport Package brakes.
This size was also used on some Miatas outside of the US after 2002. They are 9.9" in diameter, please check your brakes before ordering if you're not sure.