squirt, I had a terrible experience with that product. I was a gentle with it as could be. After 4 very light pressure passes I tightened it a bit more, though nothing really crazy, just a 'next step' of pressure and it cracked apart like an egg.
I had to very very very carefully use needle nose pliers to extract the five pieces in the spark plug hole. Dropping a piece into the cylinder would have been super bad because I wasn't near a shop and didn't have a magnet. It was like playing that old kids game "Operation". Not fun.