12T pinion.
http://store.rc4wd.com/Bully-Comp-22-Front-Rear-Axle_p_455.html
Parts as listed at the axle kit.
"What's included:
- 1x Bully 2 Front Axle with knuckles
- 1x Bully 2 Rear Straight Axle
- 2x Upper 4 links mount
- 4x Lower 4 links mount
- 2x Motor pinion gears
- 2x Clear dusk cover
Important Note: The gears don't come pre-lubed. You will need to remove the front cover and use your preferred lubrication or part # X-0317 (Monster Lube)
Optional Parts:
Steering kit with servo mounts (Part # X-0404)
Replacement Parts:
Bully XVD Axle Shaft (Part # X-0277)
Bully straight Axle Shaft (Part # X-0151)
Bully replacement gears (3) (Part # X-0163)
Bully bearings (Part # X-0326)
Bully axle housing parts (Part # X-0492)
Bully pinion gear (Part # X-0248)
Bully screws (Part # X-0259)
This axle is designed to fit any type of wheels that has a 12mm back hex.
To get more width, you can use 12mm widener (X-0132)"
http://store.rc4wd.com/Bully-12T-Pinion-Gear_p_93.html