My tire was leaking slowly and I found the source was a small nail or staple. Thought I'd give it a try as the promotional videos show it works on most flat tires. The dealer would probably sell me a new tire, so what do I have to lose? The first attempt to plug in failed. The plug went through but then broke off (at the brass tip) and most of the plug remained in the tool when I removed it from the tire. It was a preloaded fork. I put a new plug in the instrument and tried again. You have to put the plug in the same hole (obviously), but the sharp puncture angle meant I had to drive through more tires. It took all my strength and body weight to penetrate the belt. But it worked the second time! Your mileage may vary. Overall this is a well made tool and the force required to pry through a tire belt must be considered. The candles seem overpriced but they do the job. I cut off the excess, reinstalled the wheel and have been driving the car for a week with no leaks.