As you can see in the photo I had to put a lot of JB Weld on the end that screws into the spark plug hole. The reason for this is that this ending rotates. I put it in the spark plug hole and tightened it slightly and when I tried to take it off the hose twisted and the threaded part didn't come out. And you can't get pliers/tools on the threaded part to pull it out. Luckily I was able to put enough JB Weld on it and let it dry for it to come out. When I got out I completely covered it with JB Weld to keep it from happening again. Poor design, threaded end and hose MUST NOT ROTATE. It must be an anti-twist connection. If this were to happen with a deep spark hole compared to a typical 80's V8, the head would have to be taken off the car to remove the tester. In addition, the sensor is extremely unreliable. Don't even think you're going to follow the caliber instructions. I couldn't work from scratch like you should be able to. The only way to get stable readings is to start in the 45-55 range. It won't go back to zero if you start at zero, but it's okay to go back to 45/55 if you start at 45/55. As the saying goes, "You get what you pay for." And I'm sure that's why many of these tools cost so much more than this one.