Rpm Module/Chip Tester MSD IgnitionIf you're using an MSD ignition box or rpm module, you need to have one of these rpm checkers. Each tester operates on a single 9 V battery and is simple to use you just plug it into your MSD ignition box or rpm module and hold down the buttonthat's it. MSD rpm module testers are essential for any racing class with rpm limitations. User friendly plug and play design Details: Emission Code: 5