i have 3 coils now with 3 different plug fitting on each one. they are just for easier swapping that's all. plus i now also have another pi machine that has a 3 pin connector fitting on it. so it allows me to swap the coils around when needed easier. i also thought, if i was to say borrow a coil and it had a 4 pin plug fitted and i had only a 3 pin on the machine. i don't think they would like the thoughts of me asking if i could change the plug on there coil first before i could use it.