You know what a car looks like without hub caps - same with your mobile engine. Rubbish, and not only that, the wheels will fall off! These Hub Caps fit the larger diameter axle such as the rear wheels of the Traction Engine and the Steam Roller.
You know what a car looks like without hub caps - same with your mobile engine! AND THE WHEELS WOULD FALL OFF.......WHOOPS! These Hub Caps fit the smaller diameter axle such as the front wheels of the Traction Engine and the Steam Roller.