In addition to what was said above I want to just interject, in case you were un aware, that you need to run these with a prop. If you run them without a prop they could over-rev and self destruct pretty quickly. When you pick one you want to test run check back here for a recomended prp size that will put the right load on the engine... too big will lug it down and too small will allow an over-rev. If you already know this, I appologize but I would hate to see these engines destoyed.