The numbers are as follows.......
All drivers are white internal/external, and very good quality.
9 tooth #504152503 2.52" pitch
10 tooth #504152502 2.52" pitch
these drivers are appx. $50 US each
Note 8 tooth Doo drivers are available but they are 3" pitch.
8 tooth #504152552 3" pitch, do not use unless you convert to a 3" pitch track!!!!!!!!