Re: help please lol
Spark plugs are made pretty much the same way... the threaded part that goes into the engine and the other end which is outside the engine and gets the spark plug wire attached to it. That end of the spark plug is also threaded and sometimes there is a little round nut on those threads. If you can see threads on the end there's no nut. If you can't see threads then there is a nut. Some rubber boots (the part connected to the wire which fits over the end of the spark plug) are set up for a spark plug with the round nut on it and some are smaller and are to fit on the plug with the nut removed. Our kits are set up for the smaller diameter, the threaded end with the roundish nut removed. Simple.
Someday when I grow up I will probably lose interest in toys with wheels, but until then...