This is one cool item! Our new KOSO Mini Recall Tachometer is the perfect tach for your Mud Motor it will allow you to see the RPM while running and has a peak RPM recall which is perfect when trying to find the right Prop Pitch Just wrap the single wire around the plug wire and you're ready to go! The tach can be programmed for any spark pulse. Tach size is 1 1/4 X 2 1/4. Comes with mounting hardware.