Under normal circumstances, first-tier cities, from five or six thousand to seven or eight thousand, have to go to processing plants if they exceed 10 thousand.
Second-tier cities are still more than four or five thousand.
There are more than 3,000 third-tier cities.
The fourth line goes to the city, because it is not easy to find, and there can be more than 3 thousand.
The above treatment is more pertinent, because we are jewelry makers and we will know the situation everywhere.