Rear wheel includes:

• 80 tooth sprocket (nominal 1/4" pitch chain)
• Free-wheeling ratchet.
• 2 X ball bearing
• 12.5" X 2.25" tyre (Max 50PSI)
• 170mm X 12mm axle with threaded reduced ends (each end is 10mm dia. for a distance of 24mm, includes nuts, washers and spacers). Measurements and photo may differ slightly.  

The sprocket and ratchet can be reversed and refitted to the other side of the wheel if needed.

This would be useful for driving 2, 3 or 4 wheels on an electric vehicle etc.