Powerbuilt 641148 12mm Back-Tap Thread Repair Tool
The back-tap's patented collapsible design allows it to engage be placed through the spark plug hole and into the chamber. A mandrel is then drawn back, expanding the tool's threaded area and threading into the clean threads at the bottom of the spark plug hole. The Backtap repairs the damaged threads as it is drawn up through the spark plug hole, bringing debris and metal filings with it. Made in USA and comes with a lifetime warranty.