The pitch is 48-metric, and it has 70 teeth. The new one they'll release for it will be 105T at the smaller .6 module for a much larger range of ratios.
It comes with a 22 tooth pinion, and it's fine for most stock racing, silver can or sport-tuned, i believe. Anything like 19 Turn and less will need maybe 20T and smaller, though I don't know how small it will allow...
If you've had a Tamiya kit before, you'll probably have a 19T pinion somewhere...