Like I said earlier, the tool is designed to check the timing through the spark plug hole without the degree wheel if you know where the coil fires on the flywheel. Nothing new, two cycle used to do it all the time. If I have a problem on the Dyno or at the track it is Handy to let me know if I have a timing problem or not. To the poster who said nothing more accurate than a timing light. I think I know that and so do all the other readers however using a light at the track is time consuming and this is a Time saver. Screw the insert in the sparkplug hole, set the dial indicator in the insert. Roll the engine to tdc compression stroke. Set dial indicator to "o". Remove air shroud. Roll the flywheel to where you know the firing point is ( most generally right coil leg lines up with slot in flywheel.). I always mark my engines when I build them. Count how many thousands the dial indicator travels to your match marks. Cross reference to the chart I designed and you have your timing. I will call the company to find the cost of the pieces I need and let everyone know the cost of the tool if anyone wants to purchase one.