I bought 6 for parts. Repaired 2 Hondas. I have 4 left. They're so easy to install, you don't even have to install all 6. If your machine is ever missing, simply find out which one is missing by unplugging one at a time. If it doesn't matter, it's bad. The Honda's rear coils don't require removing the intake manifold, so they're just as easy as the front 3.