For the uninitiated: this little wheel is part of a bicycle rear wheel gear shift mechanism:
As such, it is a variant of a roller chain sprocket, albeit on a special small scale (pitch = 1/2").
If you want to eventually animate this, I’d like to advise to be very precise with the surfaces which come into contact with other (moving) parts, like for instance the chain. The “gaps” of this jockey wheel could be modeled more generously, imo. I used a self written little .js script for the contour, while making it 3D in Blender. Maybe you’ll want to view the opening post of the above linked thread.