If this test were given 2 years ago or so Fish would have aced it. The tester with the nut in the end of it is what was to be used for CD or HEI ignition and should have HEI right on it. The one without the nut was used for non CD ignition. Kohler has since discontinued the one with the nut and say to use the one without the nut for everything as of about 2 years ago. I personally have seen a bad CD ignition module fire the tester without the nut and not fire the tester with the nut and it would not run the engine. I still feel both testers should be made but that is just my opinion.