Two pieces, enough for one rear wheel.
The RUMBLERS wheels are each two separate pieces, the inside and the outside wheels. They are securely attached to the RUMBLERS axles with a large stainless steel screw. The wheels have an octagonal recess for the axles octagonal shape, and that maintains a solid connection to the motors with no slippage. The outside of the wheel can be accessed with the wheels upright.
The inside of the wheel can be accessed with the wheels lying flat.