If you can still find this driver, it's a great alternative to the Seas Lotus Reference or Excel magnesium drivers. The model # is W17E-001. It is especially appealing to those who love the sound of the Lotus, but prefer something a bit easier to use and less brutally revealing.
Distortion is very low, and the top end is smooth and plays flat out to about 4-5khz. One of my favorite drivers. You could use this in the car without any lowpass filter.
Compared to the Lotus reference, the bass is nearly identical in performance. The midrange too has that strikingly clear and vivid character, yet is not quite so analytical and cold (or revealing for that matter). Dynamics is superb and like all Excel drivers it holds its composure well at high output, without audibly straining or breaking up.
Compared to it's cheaper cousin the G18RNX/P, it doesn't have the sheer bass output or effortless quality when reproducing low frequencies. However, the midrange is a noticeable step up in terms of clarity, sounding more open and realistic. That's not to say the G18 is not a good performer, but the midrange is not as precise and tends to sound more washed out.
The only caveat with the Excel is that the fiberglass cone is covered with a resin of some sort that's used to stiffen the cone. In high temperatures, the cone may become soft and flexible possible leading in a decreased performance and/or permanent damage.