Like everything else we offer, this is "fully tested". There is nothing I hate worse than taking the time to drive to a tire repair shop and watching them repair my flat, when I know I could do it myself in a tenth the time. It's easy to plug a nail or screw hole: pull out the nail or screw with the pliers, take the knurled reaming tool and put a little lube on the tip to clean out the hole. Next, insert the end-slot needle with a plug attached and, voilá! You're heading down the road faster than you can say, "What an awesome day!" The kit includes pliers, a marking crayon (so you can act like the pro tire guys), lube for the reamer, a utility knife to cut off the excess plug, reamer and end-slot needle, and 25 plugs. All this comes organized in our Water-Resistant Trunk Bag. Purchase one for every car and put it in your trunk today. Try not to smile the next time you have a flat tire.