I have the TNC but the tach that is connected to the engines are great. Until you want a tach for another plane that doesn't have the on board unit. I was fooling with a DLE last week with the ignition tach, I really liked it!! If I was getting a new engine with the ignition plug for one I would order the tach at the same time. Joe and I were talking aBOUT THEM AND HE BROUGHT UP THE USE OF THE ON BOARD FOR TWINS, great idea, would make life easier. It never even crossed my mind.