Welcome. You will need to order a blade plug additionally. As for length, it's a bit of guess work. Read the description of the emitter, it tells you its length. From that, you can estimate how far deep the blade plug may need to be. Or alternatively, get a long blade plug and then you can cut it to get get the right length. (You will need a tube cutter for that. I have not tried it before but have read it can be done).