New 2001 is300 Lexus 4dr

I would like to say hi and to ask a question on the different types of lengths there are and why on spark-plugs for this particular model. I believe it has something to do with type of model it is and where it was made to be used in Europe as the entry to competitive brands. FK20HR11 was the plug taken off yet all auto stores and Toyota parts specify a smaller plug. Why is this the case.