After the wire thread insert is installed, the threaded hole tolerance zone depends on the wire thread insert surface manufacturing tolerance and the wire thread insert mounting hole thread tolerance zone. The former is controlled by the wire thread insert manufacturer, and the latter mainly depends on the tapping of the wire thread thread insert mounting hole. Thread accuracy usually forms 6H level. When the accuracy is high, it can reach 5H and 4H level tolerance zones. The unified thread standards are 2B and 3B. Corresponding plug gauges can be used to measure bottom hole threads perform testing.