There is no spec for 12x media, so you probably won't see any rated at 12x. What you'll get is a drive capable of writing to 8x media at 12x speed. In some cases, any 8x disc will write to 12x regardless of write quality. In a case like Plextor, only certain media brands are deemed consistently high enough in quality to write at 12x. The remainder will write at 8x or lower.